Answer:
B,b‒a is a positive.
Step-by-step explanation:
if a=‒x x=rational number
b=x
let's see these by examples
A,a‒b is a positive, ‒x‒x=‒2x (the answer is negative) so this is wrong
B,b‒a is a positive, x‒(‒x)=x+x=2x (the answer is positive)so this is correct answer
C,b+(‒a) is a negative,x+‒(‒x)=x‒(‒x)=x+x=2x(the answer is positive)so this is also wrong
i hope it helps you