English one word substitutions for all competetive exams part 2

Which one is a nucleophilic substitution reaction among the following ?

In a group of 50 people, 35 speak Hindi, 25 speak both English and Hindi and all the people speak at least one of the two languages. How many people speak only English and not Hindi? How many people speak English?

In a group of 50 people, 35 speak Hindi, 25 speak both English and Hindi and all the people speak at least one of the two languages. How many people speak only English and not Hindi? How many people speak English?。

A binomial nomenclature has words/parts

Give one word for the following: The central part of a flower.

The letters of the word ZENITH are written in all possible orders. How many words are possible if all these words are written out as in dictionary ? What is the rank of the word ZENITH?

Given is a diagram of a bacteriophage in which one of the options all the four parts, a, b, c, and d are correct.

Given below is the diagram of bacteriophage. In which one of the options all the four parts A,B,C and D are correct?