Husband, Wife and Mailman

Question: A married couple went to the hospital to have theit baby delivered. Upon their arrival, the doctor said he had invented a new machine that would transfer a portion of the mother's labor pain to the baby's father. He was asked if they were willing to try it out. They were both very much in favor of it. The doctor set the pain transfer to 10% for starters, explaining that even 10% was probably more pain than the father had ever experienced before. However, as the labor progressed, the husband felt fine and asked the doctor to go ahead and kick it up a notch. The doctor then adjusted the machine to 20% pain transfer. The husband was still feeling fine. The doctor checked the husband's blood pressure and was amazed at how well he was doing. At this point, they decided to try out for 50%. The husband continued to feel quite well. Since the pain transfer was obviously helping out the wife considerably, the husband encouraged the doctor to transfer all the pain to him. The wife delivered a healthy baby with virtually no pain. She and her husband were ecstatic. When they got home, the mailman was dead on the porch.

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?

Question: What can be broken but never forgotten?

Question: Which thing that comes once in a year, twice in a week?

Question: You are trying to get your chicken, fox, and wheat to the barn. However, the barn is on the other side of the river. You are on a boat and can only transport one animal or wheat at a time. You must choose carefully not to leave the wrong two together, though. It's either the fox will eat the chicken or the chicken will eat the wheat. How do you take each thing across safely?

Question: During what month do people sleep the least?