I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

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.

What is the centre of gravity?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

What is the largest number you can write with just 3 digits?

Andrew sees a very rare bird named "Ruppell's vulture". Soon Andrew was dead. Can you explain the mystery, Mr. Sherlock?

There was a strange boy who was born before his father. How can this be possible?

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

Can you find a seven digit number which describes itself. The first digit is the number of zeros in the number. The second digit is the number of ones in the number, etc. For example, in the number 21200, there are 2 zeros, 1 one, 2 twos, 0 threes and 0 fours.

Solve the equation by replacing the alphabet with numbers.

MOM + MOM + NO = BOOK=