Logic Riddles

Question: Why are pianos hard to open?

Question: What animal can jump higher than a house?

Question: Why are the floors of basketball courts always so damp?

Question: What begins and has no end, and ends all things that begin?

Question: In 2000, a 40-year-old doctor told his son that, when he was a little boy, he decided to be a doctor after seeing on the internet a heart transplant being performed on a puppy with a defective heart so that the puppy could live a normal life. The boy then thought about being a doctor too someday so that he could help people in a similar way. What's wrong in this story?