What am I?

Question: I can fly like a bird not in the sky which can always swim and always dry. I say goodbye at night and morning hi I'm part of you what am I? I follow and lead as you pass. Dress yourself in black my darkness lasts. I flee the light but without the sun. Your view of me would be gone.

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: Surrounded by life , yet life is its biggest enemy. But without life there is no need for it to exist. What is it?