Can you find out which options fits best with the missing column?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

Forwards I am heavy, backward I am not. What am I?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

It is a 5 letter word if you take away first letter it is something you get from sun, if you remove second letter you will get something to eat, if you remove third letter you get a word you use in pointing at and if you remove the fourth letter you get something to drink. What is it?

Only one colour, but not one size,
Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
What is it?

Move three sticks of the spiral below to form a square.

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

What is the word or phrase?