1. ENACTS
2. ASCENT
3. STANCE
4. SECANT

November, the next month in alphabetical order starting with July.

On a microwave. Most microwaves will run for a minute if you enter 100, but will run for a minute and 39 seconds if you enter 99.

100 is also less than 99 in an ordered ranking, where 1 is first, and 100th is a lower rank than 99th place.

The years are B.C., so 2015 came before 2010.

Hen. The words are the last in each phrase from the children’s nursery rhyme.

One, two, buckle my shoe;
Three, four, Shut the door;
Five, six, Pick up sticks;
Seven, eight, Lay them straight:
Nine, ten, A big, fat hen;

This is becomes a self-referential paradox. Both A and D would be correct if there were four unique answers, but since A and D are the same answer, the chance that you would choose a correct answer is 50%, which makes B correct. But if there’s only one correct answer, the odds of choosing the correct one at random goes back to 25%. And around and round you go.

There’s a lot of discussion at Richard Wiseman’s blog and more at Lifehacker, where I first saw this.