What Deficiency does the below rebus represent?

VIT_MIN

I have four wings but can't fly.
I express no emotions.
I am found on the exact spot every time you look.
I keep toiling away with a little sound.

Do you know what am I?

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

What is next number in the pattern below:

131 517 192 123 ?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Which tank will fill first?

I have branches, but no fruit, trunk or leaves. What am I?

The following alphametic has only one solution. Can you find it?
ENLIST + SILENT + LISTEN = ANAGRAM

PS: You may start the number from 0.

Joseph buys three kinds of chocolates for 100 rupees. The first one is priced at 5 rupees, second one at 3 rupees and third one at 0.5 rupees.

If he bought 100 chocolates in total, how many pieces do you think he bought each chocolate?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?