以下关于病毒的描述中，不正确的说法是

A．对—于病毒，最好的方法是采取“预防为主”的方针

B．杀毒软件可以抵御或清除所有病毒

C．恶意传播计算机病毒可能会是犯罪

D．计算机病毒都是人为制造的

Tom has been here ______ just one year, but his father has worked here ______ ten years ago.[ ]

A. since; for

B. since; since

C. for; since

D. for; /