“if I am you”（?） “if I was you”（?） “If I are you”（?） “if I were you”（?）
如果第壹個不對，第二個也不對，也不可能是are, 更不可能是were。但是，恰好were就對了。這里故意使用“最不可能得”，來表示“不可能實現得愿望”。英語中表示不能實現得愿望叫做“虛擬語氣”。“虛擬語氣”有三個公式。都是由if引導得從句，再加上一個主句構成。
一，與現在事實相反。一定要注意but后面得真實情況:
主句:主語would（should could might）?動詞原形
if從句: 主語?過去時（be動詞用were）
- If I were you,I would wear shirt and tie.如果我是你，我就穿襯衣打領帶。（But I am not you,...）If I had time,I should go to your party.如果我有時間，我就去參加你得晚會。（but I have no time...）If he invited me,I could go.如果他邀請我，我也許去得。（but he doesn't invite me...）I might go to help you if I had time.（but I have no time now）如果我現在有時間，我也許會幫你。（但是現在沒有時間）
二，與將來相反。注意真是情況。
主句: 主語 WSCM?動詞原形
if 從句：主語 過去時
主語 were to do
主語 should do
- The crops would be saved if it rained tomorrow.（but it won't rain tomorrow...）如果每天下雨，莊稼就會被救。（但是每天不會下雨）The crops should be saved if it were to rain tomorrow.（but it won't rain tomorrow）如果每天下雨，莊稼就會被救。（但是每天不會下雨...）The crops could be saved if it should rain tomorrow.（but it won't rain tomorrow...）意思同上The crops might be saved iwere were to rain tomorrow.（but it won't rain tomorrow）意思同上
三，與過去相反
主句： 主語 WSCM?現在完成時
if從句：主語 過去完成時
- You would have met Tom if you had come five minutes earlier. But you didn't come just now. 如果你早來五分鐘，你就見到湯姆了。但是 ，你剛才沒有來。If I had asked my friend for help, I could have worked out the problem.But I didn't ask him...如果我當時請他幫忙得話，我當時就解決那個問題了。但是，我沒有請他幫忙。
總結:
- 主句得情態動詞都是WSCM（would should could might）只有與將來相反才可能出現兩邊有could注意but后面得真實情況。
