Which sentence is a run-on sentence?

ASome tortoises are huge, you can ride on them.
BBald eagles build nests of branches; the nest may weigh tons.
CA lion can run faster than a greyhound or a fox.
DHumpback whales sing songs; they sing new tunes every year

Verified Answer :

it would be A because it just, well, runs on. b states a fact. c is also a fact. d is also a fact. A IS a fact, but it does not have an and or even.

i hope that helped (and made since) ;)