練習步驟：
step1：劃分句子結(jié)構(gòu)，找句子主干
step2: 確定修飾詞，修飾短語或修飾從句的修飾關(guān)系
step3: 確定代詞指代對象
劍橋雅思9
Reading Passage 1
長難句：The drug is derived from the bark of the cinchona tree, native to South America, and by 1856 demand for the drug was surpassing the available supply.
step1：劃分句子結(jié)構(gòu)，找句子主干
step2: 確定修飾詞，修飾短語或修飾從句的修飾關(guān)系
step3: 確定代詞指代對象
劍橋雅思9
Reading Passage 1
長難句：The drug is derived from the bark of the cinchona tree, native to South America, and by 1856 demand for the drug was surpassing the available supply.