All of the flowers now raised here have developed from those in the forest. A. once they

问题补充：

All of the flowers now raised here have developed from those in the forest.

A. once they grew

B. they grew once

C. they once grew

D. once grew

答案：

A. once they grew

B. they grew once

(答案→)C. they once grew

D. once grew

解析：

C。先行词是 those，可视为 those flowers 之省略。they once grew 前省略了关系代词 which。全句意为：这儿所养的花是由他们曾在森林里种植的花培养出来的。