Grammar Questions

Hey guys,
Could someone please explain these two for me?

Because fifteenth century explorers could for the first time accurately calculate latitude and thus determine a ship’s position on the open sea, (it allowed explorers to venture) far beyond coastal waters.
A) same
B) it allowed them to venture
E) they could venture

I have a feeling that you can’t say Because… it, but I’m not sure.

Startled by the canoe’s approach, the ducks suddenly took “flight, their wings flapped” wildly as they struggled to lift themselves above the surface of the lake.
A) same
B) flight, their wings flapping

Is it B because the original is a run-on?

Yeah, no antecedent for “it” in the first Q.

Second Q you’re also correct: the original is a comma splice (IC,IC).

Yep it is a run on

“fifteenth century explorers” are a “they”