Question

My parents will take me to the park if they ____ tomorrow.

My parents will take me to the park if they ____ tomorrow.A.will have free B.are free C.will be free D.have free

Answer 1

选B

一般现在时表将来

这边给你列举if的用法

1. (表示条件)如果 ,主句用将来时，if从句用现在时表示将来
   Tom will come if you invite him.
   如果你请他,他会来的。

2. if表 是否 = whether
   I wonder if she is ill.

   （这边提醒，如果有nor，只能用whether）

3. 虚拟语气 (表示虚拟)假如,要是
   1）时态：可以表示过去，现在和将来的情况。它的基本特点是时态退后。
   a.  同现在事实相反的假设。
   句型 ： 条件从句     主句
      一般过去时   should( would) +动词原形
    If they were here, they would help you.
   
   b.  表示于过去事实相反的假设。
   句型： 条件从句      主句    
     过去完成时    should(would) have+ 过去分词
    If she had worked harder, she would have succeeded.  
    The rice would not have been burnt if you had been more careful.  
    If my lawyer had been here last Saturday, he would have prevented me from going.
   
   If he had come yesterday, I should / would have told him about it.
    含义：He did not come yesterday, so I did not tell him about it.
    If he had not been ill and missed many classes, he would have made greater progress.
    含义： He was ill and missed many lessons, so he did not make greater progress.
   
   c.  表示对将来的假想
   句型：  条件从句       主句
       一般过去时      should+ 动词原形
       were+ 不定式     would + 动词原形
       should+ 动词原形
   If you succeeded, everything would be all right.
   If you should succeed, everything would be all right.
   If you were to succeed, everything would be all right.

参考来自： http://zhidao.baidu.com/question/410832945.html?loc_ans=1002481567

Answer 2

〔选择〕B. will be free
〔解析〕
1、free 是形容词，表示处于 “有空的” 状态，不能用作have 的宾语，所以 A 和 D 两项不符合语法，不能选择。
2、if 引导的是条件状语从句，是对将来情况退一步假定，既然的退一步，就需要从将来退回到现在，也就是人们常说的 “主将从现” 原则，所以只能现在 are free。

Answer 3

选B。一般将来时在从句中用一般时态表示。

Answer 4

选B，状语从句中，主句用将来时，从句要用一般现在时。这个是语法，记住了以后做题就方便了。