We learned________some history last week.
A:about
B:from
C:for
将番茄和水稻分别培养在含Ca2+、Mg2+、Si4+的培养液中,一段时间后,测定培养液中3种离子的浓度,结果如右下图所示。该实验的结果不能说明
— How long has the train been away?— Sorry. I don't know. By the time I got here, the train ________.
“赤地千里,饿殍载道”“……蔽日,声如雷,食尽稼,赤地如焚”的写照描述了哪种自然灾害( )
以下行为能正确体现合作与竞争关系的是( )
下列关于家庭电路和安全用电说法,其中正确的是