Group 1
Group 2
Group 3
Group 4
100

If you have it, you want to share it. If you share it, you don't have it. 

What is a secret?

100

What (food) has no beginning, end, or middle?

A doughnut.

100

You answer me, though I never ask you questions.

What is a (tele)phone?

100

The highest mountain on earth before Mount Everest was discovered.

What is Mount Everest?

200

The more you have of it, the less you see. 

What is darkness?

200

It has to be broken (that's "cracked") before it can be used.

What is an egg.

200

It goes up and never comes down.

What is your age?

200

It is harder to catch the faster you run.

What is your breath?

300

It is tall when it is young and short when it is old.

What is a candle, or a used pencil.

300

The more it dries, the wetter it gets. 

What is a towel, or a sponge?

300

It is always in front of you but can’t be seen.

What is the future?

300

It stays where it is when it goes off.

What is an alarm clock?

400

It gets whiter the dirtier it gets.

What is a chalkboard?

400

The number of bricks takes to complete a building made of bricks.

What is one?  The last one.

400

It only has two words, but contains the most letters of all.

What is a post office?

400

You heard me before, yet you hear me again. Then I die, 'til you call me again. 

What is an echo?

500

How many letters are in the alphabet (in standard English)?

What is 11:  t-h-e-a-l-p-h-a-b-e-t !

500

A question that you can never answer yes to.

What is "Are you asleep"?

500

It is as big as a plate, as deep as a cup, but not even water can fill it up.

What is a (pasta) strainer?

500

The value of the moon (in US coinage terms).

What is $1, because the moon has 4 quarters.