Which is true about the ROUND,TRUNC,and MOD functions?

A、
ROUND(MOD(25,3)-1) and TURNC(MOD(25,3)-1) are both vaild give the same result
B、
ROUND(MOD(25,3)-1) is invalid
C、
ROUND(MOD(25,3)-1) and TURNC(MOD(25,3)-1) are both vaild, but give different result
D、
TURNC(MOD(25,3)-1) is invalid