Before the search party reached the scene of the accident, “the rain began to fall “, making the rescue effort more difficult.

Explanation
 Before the search party reached the scene of the accident, "the rain began to fall " , making the rescue effort more difficult. eliminates an error in the sentence  Before the search party reached the scene of the accident "The rain had begun to fall"   making the rescue effort more difficult. اس سے پہلے کہ سرچ پارٹی جائے حادثہ پر پہنچ جائے "بارش شروع ہو چکی تھی" جس سے بچاؤ کی کوششیں مزید مشکل ہو گئیں۔ *** "had begun" in the past perfect tense.  the past perfect indicates that the thing happened and was completed. such as "the rain is starting and fall" so we use "had begun" here to make a meaningful sentence ND16-8-2023