When it's bad luck to meet a black cat?

I am the fastest animal but cannot climb the tree. What am I?

I am a five-letter word and comprises two different vowels and three same consonants. I am so strong that I can spoil your entire work.

Can you find out who am I?

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

If six children and two dogs were under an umbrella, how come none of them got wet?

John is looking at Jenifer, but Jenifer is looking at Jacob. John is married, but Jacob is not.

Is a married person looking at an unmarried person ?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not-rounded numerals equals 24.

What do you call a fish without an eye?