英文原文：

Hi! I'm Tim from BBC Learning English and today I'm going to tell you about three useful words:?because,?as?and?since.

These are all used to give reasons.

Because?is more common than?as?or?since?and we use it when we want to focus on the reason.?I'm tired?because I didn't sleep very well.

When we want to give extra focus to the reason, we can put the?because?clause at the beginning of the sentence. Because my bed is uncomfortable, I'm getting a bad back.

As?and?since?are more formal than?because?and we use them to focus on the result rather than the reason.?I hope Tom's brought that comic?as I wanted to borrow it from him.?Noodles are popular?since they're easy to cook.?

We often use?as?and?since?clauses at the beginning of the sentence. Just remember to add a comma. So,?as our minute is up, I'll finish recording this video.

中文翻譯：

你好！我是來自BBC Learning English的Tim，今天我要告訴你三個有用的單詞：because、as和since。

這些詞都用于表示原因。

Because比as或since更常用，我們使用它時想要專注于原因。我很累，因為我沒睡好。

當我們想要更加關注原因時，可以將because從句放在句子開頭。因為我的床不舒服，我背痛了。

As和since比because更正式，我們使用它們來強調(diào)結(jié)果而不是原因。我希望Tom帶來那本漫畫，因為我想從他那里借來。面條很受歡迎，因為它們?nèi)菀着腼儭?/p>

我們經(jīng)常在句子開頭使用as和since從句。只需記得加上逗號。所以，我們的一分鐘時間到了，我要結(jié)束這個視頻的錄制了。

測驗：

1.?True or false: 'Because', 'as' and 'since' are all used to give opinions

A true

B false

2.Which of these sentences is incorrect?

A?Because it's a nice day, let's go outside!

B?As I'm working later than usual, let's have dinner tonight.

C?Since it's Saturday I don't have to work!

3.Which of these sentences focuses on the reason for something?

A?I failed my exams because I didn't study.

B?As she had never met him before, she didn't know what he looked like.

C?Since it's quite late, shall we get a takeaway pizza?

答案：1B? ?2C? ?3A