Murder?

Question: Romeo and Juliet are dead. The only evidence of their death is in their house, and it is some shattered glass and a puddle of water. The only furniture in the house is a bed, a dresser and a bookshelf. The house is next to a railroad track. Their only pet was a cat. How did they die?

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: During what month do people sleep the least?

Question: When is 99 more than 100?

Question: What can be broken but never forgotten?

Question: What gets broken without being held?