The letters in the series are placed such that the number of letters skipped between adjacent letters increases by a constant value. Which of the following series observes this rule?

How many pairs of letters are there in the word $DONATE$ which have as many letters between them as there are in the alphabet?

Arrange the given words in alphabetical order and choose the one that comes in the middle.

Two letters in the word $TRESENCE$ have as many letters between them in the word as in the alphabet and in the same order. Which one of the two letters comes earlier in the alphabet?

Each of the following questions is based on the following alphabet series.
$A, B, C, D, E, F, G, H, I, J, K, L, M$
$N, O, P, Q, R, S, T, U, V, W, X, Y, Z$
If the letters of the given alphabet interchange positions,so that $A$ takes the place of $Z$ and $Z$ takes the place of $A$; $B$ takes the place of $Y$ and $Y$ takes the place of $B$ and so on,what will be the thirteenth letter from the right?

Find which one word cannot be made from the letters of the given word: $REASONABLE$.