Answer :
Option (c)
Given:
The objective is to find the number of sides required to find the remaining sides in a 30-60-90 triangle.
Since, one of the angle is 90°, then it is a right angled triangle.
For a right angled triangle any one side of the triangle is enough to find the other two sides of the triangle using trigonometric ratios.
Hence, option (c) is the correct answer.