What Deficiency does the below rebus represent?

VIT_MIN

One is to three as three is to five and five is to four and four is the magic number.
What is the pattern?

Two in a corner, one in a room, zero in a house, but one in a shelter. What is it?

You stand in front of two doors. A guard stands next to each door. You know the following things: one path leads to paradise, the other leads to death. You cannot distinguish between the two doors. You also know that one of the two guards always tells the truth and the other always lies. You have permission to ask one guard one question to discover which door leads to paradise. What one question would you ask to guarantee you enter the door to paradise?

We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

Which of the eight images will fill the missing image in the puzzle below?

If you drop me I’m sure to crack, but give me a smile and I’ll always smile back. What am I?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

What question can you never answer yes to?