this is a multiple choice question

Let Q=F(K,L) denote a production function, where Q is the quantity of the good produced, K denotes units of capital and L denotes units of labor. Suppose that for each value of K, the marginal product of labor is decreasing, and for each value of L, the marginal product of K is decreasing. If we start with inputs K*, L* that are both strictly positive and change the scale, then: a) the production function F(K,L) necessarily exhibits decreasing returns to scale; b) the production function F(K,L) necessarily exhibits constant returns to scale; c) the production function F(K,L) necessarily exhibits increasing returns to scale; d) the returns to scale of the production function F(K,L) cannot be determined the information provided; e) the returns to scale are increasing over small ranges of output and then decreasing for larger ranges of output