原因狀語從句 | because、for和as的用法區別
原因狀語從句的從屬連詞because、as和for的選擇，是大家經常會碰到的問題，尤其在做完形填空類的題目時，究竟該選擇哪個，經常會困擾大家。不用擔心，貼心的小編爲大家整理了相當詳細的解析：
在because，since，as這三個從屬連詞中，以because語勢最強，since次之，as又次之。Because通常表示“新信息”，即表示一種未知的原因，而since / as則表示已知原因。所以，如前所述，在回答why-問句時要用because-分句，而不用for-分句，同樣也不用since- / as-分句。作爲分裂句中心成分，如前所述，也只能用because-分句之前可用否定詞或其他修飾語，這種分句之前還可以用某些並列連詞，但for-分句不可以，同樣的since- / as-分句也不可以。關於這一點，我們再補充例子：
I went to the state university chiefly because the tuition was cheaper.
She didn’t want to go to Africa, probably because the weather is too hot.
I’m going there tomorrow because I have to, not because I want to.
由於since- / as-分句通常表示已知的原因，所以常常出現於句首，這又是它們與for-分句用法上不同之處。
例如：
As China is a long, narrow country, the temperature varies considerably from north to south.
Since he had a certain talent for composition, his English master encouraged him to write little pieces for the college magazine.
當然since- / as-分句也可位於句尾，作爲一種補充說明。
例如：
I’ll have you ask someone else, since you can’t answer this question.
He saw her, as they were both getting off the bus at the same time.
看完了小編整理的語法解析，大家對打敗because、as和for這三個“小怪物”是不是多了幾分信心呢？趕快收藏起來吧~
