Which of the Following Production Functions Exhibit Constant Returns to Scale

Multiple Choice

Which of the following production functions exhibit constant returns to scale? In each case y is output and K and L are inputs.(1) y = K^1/2 L^1/3.(2) y = 3K^1/2 L^1/2.(3) y = K^1/2 + L^1/2.(4) y = 2K + 3L.

A) 1, 2, and 4
B) 2, 3, and 4
C) 1, 3, and 4
D) 2 and 3
E) 2 and 4