There are two character strings：s and t.s= My favor is computer ，t=substr(s，9，5)．Then the result after operation is
A．S="My favor is computer"； t="compu"；
B．S="My favor is computer"； t="is co"；
C．S="My favor"； t="is co"；
D．S="My favor"； t="is computer"；