Consider the following model: E(y) = B0 + B1*x + B2*x^2. If B2 is estimated to be positive, what does that indicate about the shape of the expected value of y?

a. There is a concave-up function (a u-shape)

b. There is a concave-down function (an inverted u-shape)

c. There is a straight line

d. There is a horizontal line.