Explanation The hertz is the unit of frequency  of one cycle per second.   symbol: hertz (Hz) Hertz in honor of the German physicist Heinrich Hertz hertz in the International System of Units (SI) frequency i s defined as one cycle per second *** Explanation Exponential notation (scientific notation) is used to express very small (e.g., 0.0000001) or very large (e.g., 1000000000) quantities compactly by representing numbers as powers of 10 . Key Information : Format : a × 10^n, where 1 ≤ a < 10 and n is an integer. Used for very large or very small numbers . Examples: Large number : 6.022 × 10^23 ( Avogadro's number ) Small number : 1.6 × 10^-19 ( Charge of an electron ) Explanation Marconi  invented  Radio . Radio was invented in  1895 . Guglielmo Marconi was an  Italian  inventor.  ***** Explanation The Mole (mol) is the SI unit of amount of substance, representing 6.022 x 10^23 particles. It is used to measure the amount of a substance in a sample. Explanation Louis Pasteur (1822–1895) was a pioneering microbiologist and chemist whose work bridged both fields: As a Chemist : Discovered molecular chirality (optical isomers). Studied fermentation, proving it was caused by microorganisms. As a Microbiologist : Developed pasteurization (heat treatment to kill microbes in food). Created vaccines for rabies and anthrax. Disproved spontaneous generation (germ theory of disease). Explanation The chemical formula CH₃COOH represents acetic acid , a weak organic acid commonly found in vinegar. Key Information : Common Name : Acetic acid (systematic name: ethanoic acid). Properties : Weak acid (partially dissociates in water). Pungent smell, sour taste (vinegar contains ~4–8% acetic acid). Explanation Xylem and Phloem are specialized conducting tissues in vascular plants: Xylem : Transports water and minerals from roots to other parts (unidirectional). Phloem : Transports sugars (photosynthates) from leaves to other parts (bidirectional). Explanation The atomic weight of Mercury (Hg) is 200.59 unified atomic mass units (u), as listed on the periodic table. Key Information : Symbol : Hg (from Latin Hydrargyrum) Atomic Number : 80 Standard Atomic Weight : 200.592 u (often rounded to 200.59 u). Explanation The mass of Earth is approximately 6.0 x 10^24 kilograms ( 5.98 x 10^24 kg ). This is a widely accepted scientific value , based on various measurements and calculations, including: Gravity measurements Satellite orbits Seismological data Planetary formation models Explanation Longitudinal Wave (Primary Nature): Sound propagates as compressions and rarefactions (particles vibrate parallel to wave direction). Example: Sound waves in air. Mechanical Wave (Medium Dependency): Requires a medium (solid, liquid, gas) to travel—cannot propagate in a vacuum. Transverse Wave (In Specific Cases): In solids, sound can also exhibit transverse wave components (particles vibrate perpendicular to the wave direction).

Explanation Negative imperative sentence → passive voice starts with "Let... not be + past participle" " Do not pay " → "Let... not be paid" Object " him " becomes the subject in passive. Correct passive voice: Let him not be paid anything.

Explanation The hertz is the unit of frequency  of one cycle per second.   symbol: hertz (Hz) Hertz in honor of the German physicist Heinrich Hertz hertz in the International System of Units (SI) frequency i s defined as one cycle per second ***

Explanation Imperative sentence → passive voice starts with " Let " Base verb " strike off " → past participle is " struck off " Structure : Let + object + be + past participle Correct passive voice: Let his name be struck off.

Explanation Exponential notation (scientific notation) is used to express very small (e.g., 0.0000001) or very large (e.g., 1000000000) quantities compactly by representing numbers as powers of 10 . Key Information : Format : a × 10^n, where 1 ≤ a < 10 and n is an integer. Used for very large or very small numbers . Examples: Large number : 6.022 × 10^23 ( Avogadro's number ) Small number : 1.6 × 10^-19 ( Charge of an electron )

Explanation Marconi  invented  Radio . Radio was invented in  1895 . Guglielmo Marconi was an  Italian  inventor.  *****

Explanation The Mole (mol) is the SI unit of amount of substance, representing 6.022 x 10^23 particles. It is used to measure the amount of a substance in a sample.

Explanation Louis Pasteur (1822–1895) was a pioneering microbiologist and chemist whose work bridged both fields: As a Chemist : Discovered molecular chirality (optical isomers). Studied fermentation, proving it was caused by microorganisms. As a Microbiologist : Developed pasteurization (heat treatment to kill microbes in food). Created vaccines for rabies and anthrax. Disproved spontaneous generation (germ theory of disease).

Explanation The chemical formula CH₃COOH represents acetic acid , a weak organic acid commonly found in vinegar. Key Information : Common Name : Acetic acid (systematic name: ethanoic acid). Properties : Weak acid (partially dissociates in water). Pungent smell, sour taste (vinegar contains ~4–8% acetic acid).

Explanation Xylem and Phloem are specialized conducting tissues in vascular plants: Xylem : Transports water and minerals from roots to other parts (unidirectional). Phloem : Transports sugars (photosynthates) from leaves to other parts (bidirectional).