Let C be the curve defined by x²y = 4. Which of the following statements is true of curve C at the point (2, 1) ?
a). It has relative minimum because y' = 0 and y'' > 0
b). It has relative minimum because y' = 0 and y'' < 0
c). It has decreasing and concave up because y' < 0 and y'' > 0
d). It has decreasing and concave down because y' < 0 and y'' < 0