—My son is addicted to computer games. He is hopeless, isn't he?

—Yes, _____ he is determined to give up and start all over.

A．if

B．when

C．even if

D．unless

钢丝绳禁止与带电的金属(包括电焊线、电线等)接触，以免烧坏或受热后降低硬度。