Logic Riddle

Question: What are the next two letters in the following series and why? WATNTLITFS__

Question: You have 20 sick sheep, one dies. How many are left?

Question: I'm 10 years old my brothers half my age now I'm 100 years old how old is my brother now?

Question: During what month do people sleep the least?

Question: When is 99 more than 100?

Question: A Japanese ship was sailing in the Pacific Ocean. The Japanese captain of the ship put his diamond chain and Rolex watch on a shelf, went to get a shower and returned ten minutes later. Now listen carefully, as I will only tell it once: When he returned, both the chain and the watch were missing!! He called the crew of his ship together. There were four of them. A British guy was the cook of the ship. The captain asked him: "Where were you the last ten minutes?" And the cook answered "I was in the cold storage room to select the meat for lunch". A Sri Lankan was the house keeping guy. The captain repeated his question to him, and learnt that the Sri Lankan was at the top of the ship correcting the flag which had been put upside down. An Indian guy was the engineer maintaining the ship. Same question, and the Indian told that the he was in the generator room checking the generator. A French guy also served on the house keeping crew. Same question, and the French told that he was sleeping after the night shift. Within ten seconds the smart captain caught the thief. Who was the thief? How did the captain find him? Source: Puzzlevilla