In the given proportion, 9 : 3 :: 36 : 12, the extremes are:-
a)9, 3
b)36, 12
c)3, 36
d)9, 12

Hint:-Before solving this question, we must know about extremes, and means.
EXTREMES: The extremes are the values of the proportion that are furthest apart when written in ratio form using a colon. For example: In the proportion a : b = c : d, ‘a’ and ‘d’ are the extremes.
MEANS: The means are the values of the proportions that are the middle terms. For example: In the proportion a : b = c : d, ‘b’ and ‘c’ are the means.

Complete step-by-step answer:
As mentioned in the hint provided above, the extremes are the values of the proportion that are furthest apart when written in ratio form using a colon.
Therefore, in 9 : 3 :: 36 : 12, the extremes are 9 and 12.
Hence, the correct option is (d) 9, 12.

Note:-Let us now know about ratio and proportions.
RATIO: A ratio is the comparison of two homogeneous quantities, or a division of two quantities ‘a’ and ‘b’ having the same units.
PROPORTION: Proportion says that two ratios or fractions are equal.