Good Riddles

Question: Half of those who read this riddle, I am your best friend.
I depend on you, but it's you I will defend.

What am I?

Question: Snow White had the dwarfs were having dinner. The dwarfs asked for more food so snow white got them more.

How many seconds did she take?

Question: I make up all literature, but I'm often sealed.

What am I?

Question: what are the next two letters in this sequence: A, E, F, H, I, K, L, M,

Question: In the harbor of a small town, there is a large boat. Coming off of the boat is a ladder reaching down so that the bottom rung is just above the surface of the water. As the tide comes in, the water rises at 1 foot every 30 minutes, and continues like this for 3 hours. If the rungs are each 1 foot apart, how many rungs are under water when the tide stops rising?