为自己加油

现在所有的人都应该知道如何操作电脑，否则，他会落后于时代。

A.
Now everyone should know how to use computer, or he will fall behind.
B.
Now everyone should know how to use computer, otherwise he will fall behind.
C.
Now nobody should know how to use computer, otherwise he will fall behind.
D.
Now everyone should know how to use computer, weather he will fall behind.