MCQs

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
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
The s tratospheric ozone layer  is Earth's “ sunscreen ”  protecting living things from too much  ultraviolet  radiation from the sun. Oxygen layer in the  atmosphere Ozone   protects  us from the harmful ultraviolet radiation of the sun. Ozone  formula : O3 The ozone layer lies approximately  15-40 kilometers  (10-25 miles) above the Earth's surface, in the stratosphere. The ozone layer is  depleting : Air pollution

Explanation
Vitamin D deficiency can cause Rickets , a disease characterized by: Soft and weak bones Skeletal deformities Stunted growth Increased risk of fractures

Explanation
A triangle has three edges Its three sides. It also has three vertices , which are each corner where two edges meet.

Explanation
A line has no end points, a ray has one endpoint and a line segment has two endpoints.

Explanation
The element of an electric stove made nicrome. Nichrome 80/20 is an ideal material, because it has relatively high resistance and forms an adherent layer of chromium oxide when it is heated for the first time.

Explanation
The word pentagon is derived from a Greek word, pente, meaning five sides or a five-sided polygon.

Explanation
Energy is measured in units of kilocalories One kilocalorie  is equal to 4.18 kilojoules. The amount of energy a food contains per gram is known as its energy density, So we can describe fat as more energy-dense than protein or carbohydrate.

Explanation
Let's analyze the statements to determine the validity of statement (iii). Statement (i): The bulb X lasts longer than bulb Y. X > Y Statement (ii): The bulb Y does not last longer than bulb Z. Y ≤ Z Statement (iii): Bulb Z lasts longer than bulb X. Z > X Combining the information from statements (i) and (ii): From (i): X > Y From (ii): Y ≤ Z To find if (iii) is true, we need to see if Z > X can be logically derived from the given statements: Since X > Y and Y ≤ Z, we can deduce X > Y ≤ Z, which means X is greater than or equal to Z ( X > Z is not necessarily true, but X > Y ≤ Z suggests X may or may not be greater than Z ). Therefore, without additional information, we cannot definitively conclude whether Z > X is based solely on statements (i) and (ii). So, the answer is " Uncertain ."