Solution:

**Choice B is correct.**

Clearly, from graph the curve increases from *x*=40 to *x*=50 and then it start decreasing from *x*=50 to *x*=60.

Hence, option B is correct.

Solution:

**Choice B is correct.**

Clearly, from graph the curve increases from *x*=40 to *x*=50 and then it start decreasing from *x*=50 to *x*=60.

Hence, option B is correct.