The British Isles（Reference for Teaching）
(4)they don't know what they do next.
答案：do前加will。本句意為；他們不知道接下來該做什么，用一般將來時。或者將“they”改為to。把賓語從句簡化為“what to do”結構。
(5)it is known to us an，the earth is smaller than the sun.
答案：“it”改為“as”。as引導非限制性定語從句，或者將“，”改為“that”。that引導主語從句。it為形式主語。
(6)the reason why he was late for school was because he got up late.
答案：“because”改為“that”。因本句型結構為“the reason…is that…”，that引導表語從句。
(7)7his is a fact that english is widely used as an international language.
答案：“this”改為“it”.在本句中“it”為形式主語。形式主語、形式賓語只用it，而不能用“this” or“that”。
(8)that you need is more practice.
答案：“that”改為“what”。因為“that”引導名詞性從句時。只起引導作用，不作句子成分.而在這個主語從句中，缺少need的賓語.所以用what引導。