If A matrix has 18 elements, then possible orders it can have

A. (1, 12), (2, 9)
B. (1, 9), (1, 18), (2, 9), (3, 6)
C. (1, 18), (2, 9), (3, 6)
D. (9, 2), (6, 3), (18, 1)
E. (1, 18), (3, 6), (3, 9)

Choose the correct answer from the options given below:

C and D only

A matrix with 18 elements must have order $m\times n$ such that

$m\cdot n=18$

Possible factor pairs of 18 are

$(1,18),\;(2,9),\;(3,6)$

(9, 2), (6, 3), (18, 1)

Hence the possible orders are exactly these.

The correct option is (C) and (D).