Find the missing letter in the last circle logically in the given below picture.

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.

Cristina was born in 1888. She just had her 30th birthday today how did that happen?

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?

Three playing cards in a row. Can you name them with these clues? There is a two to the right of a king. A diamond will be found to the left of a spade. An ace is to the left of a heart. A heart is to the left of a spade. Now, identify all three cards.

Christina is practising her dance steps along with her friends. In a particular sequence, all of them form a row. At that point, Niharika is standing in the 4th position from either end of the row.
Can you find out how many girls are practising together?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

How can you leave a room with two legs and return with six legs?

What goes up but never comes down?

Rearrange the letters in "new door" to make one word.