问题
选择题
The boy is so sad because his lovely pet _____ for four days.
A．has died
B．has been dead
C．is dying
D．has dead
答案
答案：B
题目分析：for+一段时间，句子要用完成时态，并且句子的谓语动词要有延续性。句意：男孩是如此伤心的因为他的可爱的宠物死了四天了。故选B.
点评：非延续性动词向延续性动词的转变熟记一下几个：
leave --- be away, borrow --- keep, buy --- have, begin/start --- be on, die --- be dead, leave --- be away from, fall asleep --- be asleep
2ZnO＋2SO2；鼓风炉中：2C＋O2
2CO 鼓风炉中：ZnO＋CO
Zn＋CO2
