---How did it that all the flowers died ?-I had forgotten to water them.A. come onB. c

---How did it that all the flowers died ?
---I had forgotten to water them.
A. come on
B. come up
C. come about
D. come along

A. come onB. come up(答案→)C. come aboutD. come along解析：本题的含义是所有的花都死了是如何发生的，我忘记给它们浇水了，come about表示发生的意思，与本题的意思相符，故本题选C。

好好学习下