Who can answer them ?

Let's see who can answer these questions!
1. There is a man who lives on the top floor of a very tall building. Everyday he gets the elevator down to the ground floor to leave the building to go to work. Upon returning from work though, he can only travel half way up in the lift and has to walk the rest of the way unless it's raining! Why?

2. A man and his son are in a car accident. The father dies on the scene, but the child is rushed to the hospital. When he arrives the surgeon says, "I can't operate on this boy, he is my son! " How can this be?

3. A man is wearing all black. Black shoes, socks, trousers, coat, gloves and ski mask. He is walking down a back street with all the street lamps off. A black car is coming towards him with its light off but somehow manages to stop in time. How did the driver see the man?

4. One day Kerry celebrated her birthday. Two days later her older twin brother, Terry, celebrated his birthday. How?

5. Why is it better to have round manhole covers than square ones? This is logical rather than lateral, but it is a good puzzle that can be solved by lateral thinking techniques. It is supposedly used by a very well-known software company as an interview question for prospective employees.