农谚有云：“一年之计在于春…春若不耕，秋无所望。”说明植物生产（）
A.艰苦性
B.连续性
C.合理性
D.理想性
参考答案：B
What does the speaker mean a. Mary sings the best in her grade. b. The speaker has no idea whether Mary sings well. c. Mary’s singing skills are inferior to a lot of her classmates. d. Mary’s singing skills rank the second in her class.
光导纤维有什么特点？
