Problem: How does the sentence end?

The mosquitoes were out in force for the summer so I relied on bug spray and not a citronella candle because the
Answer: candle was ineffective.

Problem: How does the sentence end?

Tanya could calculate the market value on the house but Amy could not because
Answer: Amy was a child.

Problem: How does the sentence end?

Adam used the colorful yarn to make a scarf but not Michael because
Answer: Adam was experienced with crochet needles.

Problem: How does the sentence end?

Craig had difficulty meeting new people while Kenneth did not so
Answer:
Craig was awkward when they introduced themselves to the other.