1.accepted
2.their
3.lie
4.well
5.further
I would say that there is no other living thing on earth that can react to medical testing like animals can, for example, testing it on plants wouldn't do us any good. but if you tested it on animals and it changed their hair purple or something then you gained new information that with out testing would have been unknown.
if you have options then I can help more, since it says "would most weaken"
This is true
hope this helps :)
