八年級英語下冊Review of units 4--5知識講解
review of units 4--5
一. 重點詞匯短語
1. as well as
as well as同，和，也；既……也……。
如：
john can speak chinese as well as french. 約翰會說法語，也會說中文。
it is important for you as well as for me. 它不僅對我重要，對你也是一樣。
we shall travel by night as well as by day. 我們白天、晚上都要趕路。
as well 在口語中用得很多，用法和 too 完全一樣，可以互換，通常位于句末。
如：
she not only sings also plays the piano as well. 她不但會唱歌，而且會彈鋼琴。
i can do it as well. 這事我也能做。
2. “see sb. do sth.”意思是“看見某人做過什么”，它強調動作完成了，而“see sb. doing sth.” 意思是“看見某人正在做什么”，它強調動作正在進行。
例如:
i saw him crossing the street. 我看見他正在過馬路。
i saw him cross the street. 我看見他過馬路了。
i heard him singing in the next room. 我聽見他在隔壁唱歌。
i heard him sing in the next room. 我聽見他在隔壁唱歌了。
3. worth是一個只能作表語的形容詞，意為“值……的”、“相當于……的價值的”。由于它類似介詞，須后接名詞或動名詞（有被動的含義）作賓語。
如：
the used car is still worth $200. 這輛二手車依然值200美元。
is the exhibition worth a visit/visiting？ 這個展覽會值得去參觀嗎？
it's not worth getting angry with him. 犯不著跟他生氣。
it isn't worth waiting for him. 不值得等他。
4. when/while
when 既可用于一點時間(從句的謂語動詞需用終止性動詞)， 也可用于一段時間(從句的動詞用延續性動詞)， 從句與主句里面的謂語動詞所表示的動作或狀態能同時發生或一先一后分別發生。
例如：
he wants to help people when they are ill. 他想在人們生病時幫助他們。
when he got to shanghai，the ship had already set off. 他到達上海時，輪船已經開走了。
while只能用于指一段時間(從句的謂語動詞必須是延續性的)，從句與主句里面的謂語動詞所表示的動作只能同時發生， 不能一前一后發生。
例如：
one day while they were working in the fields，some farmers saw something strange in the sky. 有一天，一些農民在田間勞動的時候，看見空中有些奇怪的東西。
while i was reading，my mother was washing clothes. 我讀書時，我媽媽在洗衣服。
這兩個詞還可以用作并列連詞。when 是“在那時”或“這時突然”(and just at that time)的意思， 用來連接兩個并列分句，有時 when分句前有逗號把前后兩個分句分開。
例如：
an arab was walking alone through the desert when he met two men.