The rate of change of a function is its slope.
The slopes of each option are:
A) 7
B) 6
C) I think the option is written incorrectly. If not, then we can take partial deriviatives using x and y which would yield 0 in each case since the remaining terms are constants.
D) (-2 - 3)/(0 -1) = 5
Therefore, the answer is A
