烟支标志不应出现（）现象。
A.残缺不全
B.重叠
C.倒置
D.以上都是
参考答案：D
---You____ part in the party on time.
--- Sorry, I was delayed by the accident.
A．are supposed to take
B．have supposed to take
C．are supposed to have taken
D．supposed to take
（1）只用一种试剂，即可以将碳酸氢钠、氯化钠、硝酸钡、碳酸钡这四种白色粉末区分开来，这种试剂是______（填化学式），并写出该试剂与硝酸钡反应的化学方程式______．
（2）赤铁矿（主要成分为Fe2O3 ）在高炉里与还原性气体反应生成单质铁的化学方程式是______．
