Answer:
Option (d) is correct.

Step-by-step explanation:
Given : A right angled triangle with given dimensions.
We have to find the value of 
Consider the given right angled triangle.
Using trigonometric ratio,
The tangent of angle is the ratio of perpendicular to the base.
Mathematically written as 
For the given triangle
, base = 21 and perpendicular = 12
Substitute, we have,

Simplify, we have,

Option (d) is correct.