实生果树和营养繁殖树的生命周期的区别是（）。
参考答案：营养繁殖树没有种子萌发这一生命活动，即没有童期
It was the third time that she_____ to this mountain village to see the children. [ ]
A. had come
B. has come
C. came
D. would come
锅炉燃烧调整试验的目的和内容是什么？
