what does the below rebus means?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

I look flat, but I am deep. Hidden realms I shelter. Lives I take, but the food I offer. At times I am beautiful. I can be calm, angry, and turbulent. I have no heart but offer pleasure as well as death. No man can own me, yet I encompass what all men must have. What am I?

Identify the 10 differences between the two given pictures.

A Child was born in Lahore, Pakistan.

Still child is not a Pakistani citizen.why ?

This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?

Four children having five rocks each were playing a game in which they had to throw the rock at a particular solid area in the water. Child 1- Succeeded in throwing three rocks at a solid area but one of the rocks sunk. Child 3 - His aim was so bad that all rocks got sunk. Child 4- He was awesome and none of the rocks got sunk. Child 2 - Was the winner but was struck by a rock in the head and died. Who killed Child 2?

There are 3 apples in the basket and you take away 2. How many apples do you have now?