Problem: It was likely that Elena but not Betty had contracted malaria because

My choice: Elena had recently traveled to a third-world country.

Problem: For the fishing trip, the fisherman packed a knife, leaving his fishing rod at home. The

My choice: fishing rod was broken.

Problem: Tanya had long fingernails while Amy's were blunt, so

My choice: Tanya had an easier time picking apart the knot.

Problem: Kyle was nervous about traveling to meet Joel for the first time.

My choice:
Joel had met many online friends before.