Answer: I would contend that the three right options are:
3) “Looks in the clouds, scorning the base degrees / By which he did ascend."
4) “And since the quarrel / Will bear no colour for the thing he is.”
5) “And therefore think him as a serpent’s egg / Which, hatched, would as his kind grow mischievous, / And kill him in the shell."
Step-by-step explanation: Just to elaborate a little bit on the answer, it can be added that these three quotations refer to what Brutus believes will be Caesar's future and dangerous actions. The quotation in option 3 is meant to illustrate Brutus's idea that Caesar will, like an ambitious young man, reach for the sky and reject those who helped him get to the top. Likewise, the quotation in option 4 is meant to illustrate his concern with Caesar's future behavior, not with his present actions. Finally, the quotation in option 5 compares Caesar to a serpent's egg; like all serpents once they have hatched, he will eventually become dangerous, hence the need to end with his life while he is still "in the shell."