seem常用于由as if/though引导的'从句中，如：
a) It seems as if it is going to rain.
b) It seems as though our plan’ll be perfect.
c) It seems as if he knew nothing about that.
d) It seems as if it was/were spring already.
[注]在这种句式中，如从句所叙述的情实现的可能性比较大，从句谓语用陈述语气
，如a,b两例；若实现的可能性较小，或根本不可能实现，从句的谓语则用虚拟语气，如c,d 两例。