常考文法:
1.假設語氣if
現在和未來都有可能發生
if+S+原V，S+will/can/shall/may+原V
陳述事實:If I wake up early,I can go to school on time.
如果我早起，就能準時去上學
If you want to get good scores,practice more!
如果你想拿到好分數，多練習吧!
If it rains tomorrow,I will stay inside the room.
如果明天下雨，我會待在房間裡

   2.與現在事實相反
     If+S+Ved,S+could/should/would/might+原V
     若為過去是動詞一慮使用were
     If I had enough money,I would buy the house.
     如果我有足夠的錢，我就會買那棟房子
     If I were you,I wouldn't do things like that.
     我若是你，就不會做那樣的事(事實上我並不是你)
     
   3.與過去事實相反
       If+S+had+Vp.p.,S+would/could/should/might+have+Vp.p.
       
       If you hadn't told me that,I wouldn't have known.
       如果你當時沒有把那件事告訴我，我不可能會知道
       If you had studied hard,you could have passed the test.