**Concept: The question tests on the basics of geometry**

**Solution: **

A new og 2021 question

We know that the external angle is obtained as a sum of two opposite internal angles in a triangle.

=> z = x + y

**St(1):-**x = 50

We do not know the value of y to figure out the value of z. (Insufficient)

**St(2) :-**y = 35

We do not know the value of x to figure out the value of z. (Insufficient)

**Combining both we have**

x=50 and y =35

Thus z = x + y

= 50 + 35 (Sufficient)

**Option (c)**