吃什么对身体好

一.
(1) at表示一天中的某时刻,不用冠词,如:
at six o'clock(在六点钟), at dawn(在黎明), at sunrise(日出时), at noon(在正午)。
I arrived at school at seven.
我到学校时是七点。

(2) at表示一瞬间或短暂的时间,如:
at that moment(在那一瞬间),
at present(目前),at that time(那时)。
Your memory is always poor at this time.
你的记忆力到这时候总是不好。

(3) at表示节日或年龄,如:
at Christmas(在圣诞节,指整个节日), at the age of ten(在十岁时)。
How could you be so forgetful at the age of ten?
你才十岁怎么就这么健忘？

二.
on表示某日或和某日连用的某一时间段,如:
on Monday(在星期一), on Friday afternoon(在星期五下午), on the morning of August the eighth(在八月八日早晨), on Christmas Day(在圣诞节,指在当天)。
You were late on Monday last week.
你上星期一就晚了。

You mean I was late on May the fifteenth?
你是说我五月十五日晚了？

三.
in表示年、月、季节、世纪、时代,与定冠词连用表示一天中某个时间段,如:
in 1996(在1996年), in May(在五月), in spring(在春季), in the 20th century(在二十世纪), in the eighties(在八十年代), in modern times(在现代), in the night(在晚上)。

Sorry, I am late, the first time in May.
对不起，我晚了，五月份第一次晚。

I got up at six in the morning.
我早上六点钟起床。

A. 以下情况多用that.
(1) 如果先行词是all, much, anything, something, nothing, everything, little, none等不定代词，关系代词一般只用that，不用which。例如：
All the people that are present burst into tears.
Is there anything that I can do for you?
(2) 如果先行词被the only, the very, the same, the last, the best等词修饰，关系代词常用that(指人时，可以用who),例如：
This is the very book that I want to find.
That is the best film that we have seen.
I was the only person in my office that/who was invited.

(3) 当先行词被all, every, no, some, any, little, much所修饰时；
You can take any seat that is free.
(4) 当先行词被序数词或形容词最高级所修饰时。
It is the first foreign book that I have ever seen.
This is the most beautiful flower that I have seen.
(5) 在there be句型中，常用that.
There is a man that lives in that village.
(6) 先行词有两个，一个指人，一个指物，关系代词应该用that。例如：
The boy and the dog that are in the picture are very lovely.
B. 以下情况用which.
(1) 当关系词前面有介词时，指物常用which.
The prize for which he worked so hard was a new bike.
He built a telescope through which he could study the skies.
(2) 非限制性定语从句指物时，多用which.
Bamboo is hollow, which makes it light.
He wrote an article, which tells us about the computer.
(3) 如果先行词本身是that时，只用which.
This is that which he bought yesterday.
(4) which还有一种特殊用法，它可以引导从句修饰前面的整个主句，代替主句所表示的整体概念或部分概念。在这种从句中，which可以作主语，也可以作宾语或表语，多数情况下意思是与and this 相似，例如：
He succeeded in the competition, which made his parents very happy.

it是人称代词,作主语或者宾语.但是从句中关系代词作主语和宾语时就不能使用it了，定语从句中引导词可以是who ，which，where，whom，that，但不能用it