在各项均为正数的数列{an}中，{Sn}为前n项和，nan+12=（n+1）an2+anan+1且a3=π，则tanS4=____
某同学用嘴对一小空瓶吸一口气，空瓶就能“挂”在嘴唇上，原因是（ ）
工效一定时，工作量和工作时间成____。
f（x）= {log12(x+1)，x∈0，1)1−|x−3|，x∈1，+∞) ，
则关于x的函数F（x）=f（x）﹣a（0＜a＜1）的所有零点之和为（ ）
Mum：Mary. ____
Mary：It's very pretty.
Assistant: ____
Mum：Yes. ____
Assistant：It's $ 99.
Mum：Oh， that's expensive.
Assistant：Do you like that blue skirt？
Mary：Yes. ____
Mum：OK. How much is it？
Assistant：It's $ 50.
Mum： ____
A. Can I help you?
B. OK. I'll take it.
C. How do you like this dress?
D. I like blue.
E. How much is it?
阅读判断，用“正确”或“错误”表示。
This is my classroom. It is not small. The windows are clean. There are many pictures in the classroom. We clean the door every day. I come to the classroom early in the morning. I do my homework in the classroom in the afternoon. I like my classroom.
