The difference between C and D is that D says II will decrease.

II. -10 - 1/(x^2)

The -10 is a constant so don't worry about that. Let's take it one step at a time. When x increases, x^2 increases. Since x^2 is in the denominator, the entire term 1/(x^2) DECREASES. Since that entire term is being subtracted from the constant, the entire expression -10 - 1/(x^2) INCREASES. If you subtract a smaller number, then your result is higher.

An increase in x results in increase in II, so C. III only is correct