Choose the correct alternative for the missing term:
$AD, EH, IL, ?, QT$

Study the following arrangement carefully and answer the question.
$O, 4, E, J, 5, T, 1, A, M, Q, 3, 8, N, I, K, 7, W, F, 6, S, 9, U, 2, Y, X$
If all the numbers in the above arrangement are dropped,which of the following will be the ninth to the left of $S$?

Choose the correct alternative to complete the series: $c _ b b b _ a b b b b _ a b b b b _ a b$

The following question is based on the five three-digit numbers given:
$513, 248, 371, 634, 167$
Which of the following is the middle digit of the second highest number among these numbers?

Find the missing letters for the given series from the given alternatives:
$ab....bbc....c....ab....ab....b$

What will come in place of the question mark $(?)$ in the following alphabet series?
$XDH, \quad VGJ, \quad TJL, \quad RMN, \quad ?$