It is important to understand the text clearly.
The first line suggest that animal testing is justified because it has been involved in the major discoveries of drugs.
However, later on it says that every new drug requires animal testing and hence, every major discovery must have had to use animal testing at some stage.
The last sentence effectively tries to ask the question:
Is animal testing necessary for checking effectiveness of drugs or for being involved in major drug discoveries?
A – Correct
This completes the question above.
B – Wrong
We are not given any information about what the wonder drugs can cure.
C – Wrong
Nothing is mentioned about whether laws about animal experimentation need to change or not.
D – Wrong
Scientists ill-treating animals is not mentioned in the text.
E – Wrong
Nothing is mentioned bout drug testing on humans.