If only tears were laughter If only night was day If only pr

If only tears were laughter If only night was day If only pr if only you were only if If only it were that if only ,if necessary only if/if 为什么If only I were abird.中的were不用was 为什么是if only I were you 而不是if only i was you only if 和 if only怎么样区别? if only 和only if 的区别 if only only if有什么区别 ONLY IF 与IF ONLY 的用法