what does the below math rebus puzzle mean?

There was an aeroplane crash, every single person died, but two people survived. How is this possible?

What Time Should the last watch show in the below figure?

Which number should replace the question mark?

What number divided by 4 is the same as that number minus 4?

On rolling two dices (six-sided normal dice) together, what is the probability that the first one comes up with a 2 and the second one comes up with a 5?

Remove two matchsticks to make the below equation correct.

How many minutes are there in Feb 2017?

Note: The shortest answer is the correct answer.

You are trapped in a room with two doors. One leads to certain death and the other leads to freedom. You don't know which is which.
There are two robots guarding the doors. They will let you choose one door but upon doing so you must go through it.
You can, however, ask one robot one question. The problem is one robot always tells the truth, the other always lies and you don't know which is which.
What is the question you ask?

What building has the most stories?