The UN________ to make peace in the world. ( )
A:wants
B:want
C:wanted
① {2x=yx+y=2 ;② {2x+y=42x2−y=1 ;③ {2x+y=4z−3=5 ;④ {x=1y=1 .
下列运算正确的是( )
己知:(i) +2 →一定条件 +H2O
(ii) +SOCl2→ +SO2+HCl
(iii)+R′OH→ +HCl