Try this option:
A. f(4)=7 - false; explanation: x=4, it means that x>0 and x²-1=4²-1=15 ⇒ f(4)=15.
B. f(1)=0 - true; explanation: x=1, it means that x>0 and x²-1=1-1=0.
C. f(-1)=2 - true; explanation: x=-1, it means that x<0 and -x+1=1+1=2.
D. f(-2)=0 - false; explanation: x=-2, it means that x<0 and -x+1=2+1=3 ⇒ f(-2)=3.