5. The shoot system of perennials can help the plants absorb less of the sun's ray.
A. Right B. Wrong C. Not mentioned
6. The theme of the second last paragraph is why the perennials can survive as plants for several years.
A. Right B. Wrong C. Not mentioned
7. Desert perennials lose their leaves after the rainy season just as trees lose theirs in wetter climates before winter arrives， but the reasons for this feature are different.
A. Right B. Wrong C. Not mentioned
【参考答案】
1. B 2. A 3. A 4. C 5. B 6. A 7. B