“一堆沙子是松散的，可是它与水泥、石子、水混合后，比花岗岩还坚硬。”这句话告诉我们的道理是 （    ）

注意：1).词数100左右；

2).可适当增加细节，以使行文连贯；

Dear Li Hua,

    As a freshman in high school,I badly need your help with my sleep problem.The school rule goes that for every dormitory（宿舍）,students are only allowed（被允许）to keep the lights on before 10:40 p.m.So we should all go to bed after 10:40.However,one of my roommates（室友）often washes her clothes as late as 11:00 p.m.,and some others even turn on their flashlights（手电筒）to do homework.The noise and the light really make it hard for me to fall asleep（入睡）,I want to tell them to stop it,but I worry it will harm our relationships.What should I do?

Yours,

Sarah

下列不属于细胞凋亡的是(   )

693﹣99≈

394+105≈

88×32≈

1780÷94≈