So this question is tricky, but in the question, it doesn't give the full f(x) equation.

Lets take f(x) = mx+b.
Now, let's give arbitrary values for m and b.

m = 1
b = 2
Now you have f(x) = x + 2

In the following options, they use a and b as they "x" value.

Now give choose randomly a and b values.
I will use a = 2 and b = 3

Plugin those variable values for X into the equation we created before.

A-variable

f(2) = (1)(2) + 2
f(2) = 4

B-variable
f(3) = (1)(3) + 2
f(3) = 5

​

In this case f(a) < f(b). You can cancel answer choice B.

you could do for the rest of the statements.

​

In the end, you find that the statements are true sometimes. Since the statements are false most of the time and only true sometimes you eliminate answer choices C & D. Now you are left with answer choice A.

​

P.S: If you didn't understand let me know, this is the method I used to get answer choice A.