Good Riddles

Question: What are the next 3 words in the sequence: j,f,m,a,m,j,j,a,s_,_, and _?

Question: You see me roll everday.

Question: When is the hardest time to catch a frog?

Question: You have bag, you put a lump of metal into the bag, then you put a lama into the bag, then you put something else into the bag, and yet the bag weighs nothing. Why?

Question: There is a man who works on Big Bentley and he keeps the clock running smoothly. One day the clock stops all together, he muttered to himself "It's going to take me all day to fix it!" and he grumbles while he works because he doesn't want to have to change the time, but he finishes by tea and he doesn't have to change the clock by even a minute. How?