Question

16．We know you're hardworking．That's because we've given you the letter．

Answer 1

分析 我們知道你很努力，這就是我們?yōu)槭裁唇o你這封信的原因．

解答 答案：We know you're hardworking．That's because we've given you the letter．   （將because改為why）
此處用在系動詞is之后，引導(dǎo)引導(dǎo)表語從句；強(qiáng)調(diào)的是"我們知道你很努力"的結(jié)果；故用why．

點(diǎn)評 本題考查了從屬連詞why和 because 的用法區(qū)別：即二者都可以引導(dǎo)表語從句，但前者強(qiáng)調(diào)結(jié)果，后者強(qiáng)調(diào)原因；如：
Tom overslept this morning．That is why he was late for work．湯姆今天早晨睡過頭了．那是他上班遲到的原因． 
Tom was late for work this morning．That is because he overslept．湯姆今天早晨上班遲到了．那是因?yàn)樗�睡過頭了．