I am white when I am dirty, and black when I am clean. What am I?

What is the coolest letter in the alphabet?

Two in a corner, one in a room, zero in a house, but one in a shelter. What am I?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

Can you tell a 3D object that has just two surfaces?

A plane crashed between the border of Mexico and America. Where do you bury the survivors?

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _

What can you catch but never throw?

A girl rode into a tourist spot out of the city on Thursday. She loved the place and decided to stay for a few days. She stayed for four days and then she left for back home on Thursday.

How can this be possible?

No matter how little or how much you use me, you change me every month. What am I?