A:《南京条约》签订
B:《马关条约》签订
C:《辛丑条约》签订
D:“二十一条”签订
完成句子
某同学从一种未知的无色溶液中检验出Ba2+、Ag+,同时溶液的酸性很强,他准备继续检验溶液中是否含有Cu2+、Cl﹣、CO32﹣、S2﹣、K+、Al3+、SO42﹣、SO32﹣、NO3﹣等离子.显然,有些离子还必须检验,你认为还必须检验的离子是____ .
Cheng Long and Li Lianjie have much _______. And they often play similar roles in the movies.
∫121x+xdx=( )