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

In this image, you can see three almost identical Doraemon images. Can you spot the odd one out from them?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

What can run but never walks, has a mouth but never talks, has a head but never weeps, has a bed but never sleeps?

Known by all without exception, Forever here, for your protection, Sometimes strong, sometimes weak, Right after the night I come - hot and chic. And while millions of miles away, I always get to you, I find my way. No life around could do without me, Can you guess what I might be?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

You walk into a room where there are three primates held in their respective cages:
1) A lion who is eating the flesh of a goat.
2) An orangutan who is playing with blocks.
3) A donkey who is sitting idle.

Who is the most intelligent primate in the room?

Count the number of triangles in the picture below:

Can you find out the total number of triangles in the given figure?

Your mother’s brother’s only brother-in-law is asleep on your couch. Who is asleep on your couch?