Read the following four expressions:
A. 5+7
B. 4−16
C. 3×12
D. 550
a. (i) Without using a calculator, state which of the expressions A, B, C and D represent rational numbers and which represent irrational numbers.
b. (ii) For each expression, give a brief reason (one or two sentences) to justify the nature of the number you have stated in part (i).