Problem: How does the sentence end?

Randy was shown how to trade stocks by Nelson since
Answer: Nelson was quite experienced in the market.

Problem: How does the sentence end?

Mary gave a framed picture as a gift to Amy because
Answer: Amy was having a birthday party.

Problem: How does the sentence end?

Justin helped Kyle in the struggle of finally getting his private pilot's license and
Answer: Kyle was grateful to him.

Problem: How does the sentence end?

Donald invited Brett to Paris because
Answer:
Brett knew how to speak the native language perfectly.