Can anyone tell me a word in the English dictionary which has a silent 'z'?

What is at the end of a rainbow?

There was once a college that offered a class on probability applied to the real world. The class was relatively easy, but there was a catch. There were no homework assignments or tests, but there was a final exam that would have only one question on it. When everyone received the test paper it was a blank sheet of paper with a solitary question on it: 'What is the risk?'.Most students were able to pass, but only one student received 100% for the class! Even stranger was that he only wrote down one word!
What did he write?

Through your logical capabilities, can you make 7 an even?

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

John was so frustrated to be the suspect of being a sleeper terrorist that he shoot himself right between the eyes with a revolver in his toilet. The revolver and the bullets were accurate. Minutes later John walks out of the toilet unharmed.
How can this be possible?

Replace the question mark in the picture below.

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

A wooden log balances equally on the scales when weighed with three-quarters of a pound and three-quarters of a wooden log.

Can you calculate the weight of the entire wooden log?

Can you solve the tricky chess rebus puzzle below by ciphering the hidden meaning?