Answer: C. This fluttery flight helps them get away quickly from predators.
Step-by-step explanation:
The first option does not tell us why Butterflies flutter but rather that Butterflies flutter in the first place.
The second paragraph again does not tell us why they flutter but rather how they are able to flutter.
The third option tells us why they flutter which is that they are trying to get away quickly from predators.
The fourth option is simply announcing that we now know how Butterflies are able to flutter.
The answer is therefore option C.