Complete the table series riddle by finding the number that can replace "??".

Who always enjoys poor health?

What does man love more than life, hate more than death or mortal strife; That which contented men desire; the poor have, the rich require; the miser spends, the spendthrift saves, and all men carry to their graves?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

Can you place three balls such that the equation shown in the picture holds true?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

In this image, you can see three almost identical Doraemon images. Can you spot the odd one out from them?

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

Make a sentence consisting of three words that have the whole alphabet.

Can you identify the hidden rebus in the image below?