15里面有____个十，____个一．

As long as we present in spreading scientific knowledge among the masses, all the strange beliefs are        to go out of our life.

计算：cos²45°+tan60°•cos30°﹣3cot²60°．

问句答句配一配。
⑴How do you feel? ____      A. No, I'm cold.
⑵What colour is it?____       B. It is an orange.
⑶What is it?____             C. It's black.
⑷How many teachers?____   D. I'm cold.
⑸Are you hot?____           E. Ten.

设等差数列 $\left\{a_n\right\}的前n项和为S_n，若a_1＝－11，a_3＋a_7＝－6，则当S_n$  取最小值时， $n$  等于(     )