……they could makethe chocolate easier to break into small pieces.
可以這樣理
Itis easier for the chocolate to break into small pieces.
（it 是形式主語(yǔ)；the chocolate和to break into small pieces是主動(dòng)的主謂關(guān)系,the chocolate 是邏輯主語(yǔ)）
可變成：
The chocolate is easier to break into small pieces.
（the chocolate 取代了形式主語(yǔ)it）
……they could makeiteasier for the chocolate to break into small pieces.
(it 是形式賓語(yǔ),easier 是賓補(bǔ)足語(yǔ), for the chocolate to break into small pieces是真正賓語(yǔ)）
可變成題中出現(xiàn)的句子：
……they could makethe chocolate easier to break into small pieces.
（the chocolate取代了形式賓語(yǔ)it,成為make的賓語(yǔ),后面to break into small pieces保持不變）
上面所有句子和結(jié)構(gòu)中都需要使用不定式,所以題目答案應(yīng)該選to break.
理解這個(gè)題目,最簡(jiǎn)單的句子是：
It is easy to learn English./I find it easy to learn English.
可以轉(zhuǎn)化成：
English is easy to learn./I find English easy to learn.