The answer is C for both because they follow the correct syntax and conventions of english to allow the reader to effectively read the sentence without confusion.
Answer:
a- Animals do not react positively to human products being tested on them as they are used to determine faults and any harm.
b- the human products often contain harmful chemicals in testing stages on animals which can lead to genetic disorders
c- because there is no definitive answer which is why they're testing to find our what is going to harm the humans
