C
Lol… It cools my eyes 🙂

Answer is 12 days.
How?
Let’s assume the thief is in cave 1 and going clockwise and you start searching from cave 13 and 12 on your first day.
Cave 13 and 11 on second day,
Cave 13 and 10 on third day and so on till Cave 13 and 1 on 12th day.
So basically the idea is to check Cave no.13 everyday so that if thief tries to go anti clockwise you immediately catch it and if he goes clockwise you will catch him in maximum 12 days (including the case where he remains in Cave 1).

‘What is a word made up of four letters’.

In other words, there are four letters in the word ‘what’.

Yet has three letters.

Although has eight.

Rarely has six.

Never has five.

A postage stamp

Heat
because you can catch cold

Horses

because all his uncles are aunts(ants)

Because she wanted to see a butterfly…lol:)

There are some possibilities:
1.The river was dry
2.A fallen tree helped the dog to cross the river
2.The water was frozen

If you don’t fix the maximum numbers of digits a number can have, then you will find infinite of them.
Like this 122222222222222222222222224
Or even larger to infinity.
So the number of such number in this case infinity