Research shows that the substances 17 these colors actually protect plants from chemical damage.
答案：(D) responsible for
be responsible for 在此是「造成、導致」而非「負責」：造成這些顏色的物質其實能保護植物免於化學傷害；capable of（有能力）、different from（不同於）、inferior to（劣於）語意都不合。
答對率 19%。
be responsible for 你只學過「對…負責」（You are responsible for your own safety.），主詞通常是人。用在事物上時意思會轉成「造成、導致」——主詞是原因、for 後面是結果：Smoking is responsible for many deaths.（吸菸造成許多死亡）。本句 the substances responsible for these colors ＝ 造成這些顏色的物質。
The colors come mainly from chemicals known as antioxidants.（這些顏色主要來自抗氧化劑）——come from 與 be responsible for 講的是同一件事，一個從結果往回看、一個從原因往前看。
account for（說明、占…比例）、be to blame for（該為…負責，專用於壞事：Who is to blame for the accident?）、lead to（導致）、result in（造成）、bring about（帶來、促成）。
be responsible for（造成、負責）、be to blame for（該為…負責）、account for（說明、占）、result in（導致）、be capable of + V-ing（有能力做…）。
The fruits and vegetables we eat often come in distinctive colors. The rich colors, 16, are not there only to attract attention. They perform another important function for the plants. Research shows that the substances 17 these colors actually protect plants from chemical damage.
The colors come mainly from chemicals known as antioxidants. Plants make antioxidants to protect themselves from the sun's ultraviolet (UV) light, 18 may cause harmful elements to form within the plant cells.
When we eat colorful fruits and vegetables, the coloring chemicals protect us, too. Typically, an intensely colored plant has 19 of these protective chemicals than a paler one does. Research on how chemicals in blueberries affect brain function even suggests that these chemicals may help our own brains work more 20. In other words, eating richly colored fruits and vegetables makes us both healthier and smarter.