定黄铁矿石中硫含量，称取样品0.3862g，最后得到BaSO4沉淀0.9321g，计

What do you do at the weekend? Some people like小题1:    （stay）at home，but others like to go for a walk or play football. My friend Jack works hard in a factory during(在……期间) the小题2:   (weekday). At the weekend, he always小题3:    （do）the same thing. On Saturday he cleans his car and on Sunday he goes with his family to a village(村庄) by car. His uncle and aunt have a farm there. It isn’t a big one, but there’re always things to do on a farm. The children help with the 小题4:    (动物) and give them their food. Jack and his wife help in the fields. At the end(结束) of the day, they are all小题5:      (hunger) and Jack’s aunt gives them a big meal.

—Where ___ your teacher from?

—Beijing.[ ]

A. is            

B. are          

C. am

根据《长途光缆波分复用（WDM）传输系统设计规范》，WDM传输设备排列时，相邻机列背与背之间净距应为0.7-0.8m。

采用装配式混凝土预制板衬护渠道有哪些优缺点？

常用的以锚杆为基本支护的联合支护形式有（）、（）、（）、（）和（）等。