The correct answer should be something like: "Gene therapy involves the use of bacteria or viruses to deliver new or modified genes to cells". That is what can be concluded based on the paragraph you provided.
Answer:
Fraction-of-occurrences of 115In isotope 
Explanation:
As we know weight of 113 In isotope is equal to the sum of product of fraction-of-occurrences of two constituents isotopes and their atomic weight
------(1)
As we know sum of fraction-of-occurrences of two constituents isotopes is equal to one.
---------(2)
Substituting the given values in equation 1, we get

Substituting this value in equation 2 we get -

11)B 12)D 13)D 14)A 15)D 16)A 17)A 18)B 19)A 20)B 21)B 22)C