[Q]: How does the sentence end?

The bagel shop sells muffins, but not donuts, because

[A]: donuts have a much lower profit margin.

[Q]: How does the sentence end?

Betty has started fixing her eyebrows with makeup rather than wax, because the

[A]: wax is too difficult.

[Q]: How does the sentence end?

The carpenter shortened the length of the board for the doorway because the

[A]:
board was too long.