棉纤维中大分子之间依靠分子引力和（）能形成多级的超分子结构。
参考答案：氢键
奇山小学四、五年级师生接受上山植树任务，四年级去了45人，五年级去了15人，两级共植树900棵，平均每人植树多少棵？
—Was Lingling born in Xiamen?
— . She was born in Qingdao. [ ]
A. Yes , she was
B. No , she wasn't
C. Yes , she wasn't
D. No , she was
