after all 和 only if 的用法每个举三个例子并请告诉我它们的用法,谢谢啦!

after all
有两个意思
a. 毕竟，终究，归根结底。
例句：1。So you've come after all.你到底还是来了
2。After all, what does it matter?归根结底，那有什么关系呢？
b.应该记住
例句：He should have offered to pay--he has plenty of money, after all.他应该主动提出付款－－他是有钱的，别望了。
only if
only if
1. 在only if 这个短语中，副词only是中心词,而从属连接词if则只是用来连接从句的，因此，它表示“只有……(才)；只有在……的时候，唯一的条件是……”的意思。例如：
I told him he would succeed only if he tried hard. 我告诉他，只有努力才能成功。
2. only if 有时也写成only...if，表示唯一的条件，但是意思不变。例如：
I will only come home if you come with me. （= I will come home only if you come with me.） 只有你跟我一起走，我才回家。
因此，根据上面的分析，课文中的句子我们也可以把它改成Yet they could get the blood only if one of the frightened children would agree to give it. 这样，句子就比较容易理解，意思也就十分清楚了：但是，只有这些受惊吓的孩子中有人自愿献血，他们才能够得到血。

after all 毕竟
. You should forgive him for his forgetfulness; after all, he is over seventy.
你应该原谅他的健忘症,毕竟他已经七十多岁了.

2. You should be charitable with him; he is a child after all.
你应该对他宽容些,毕竟他还是个孩子.
3 Don't blame him for breaking that vase; after all he is a child.
别怪他打碎那个花瓶, 他毕竟是小孩子嘛.
only if:
只有当(只是在...的时候)
1. The company will succeed only if it have sufficient backing.
只有当该公司获得足够的资助,它才会成功.

2. A compound proposition that has components joined by the word and or its symbol and is true only if both or all the components are true.
综合命题由和或其符号所连接的子句组成的复合命题,只有当所有子句为真时,该句才为真

3. I can buy the house only if a mortgage for 2000 dollars is available.
只有拿到两千美元的抵押贷款,我才买得起那栋房子.