be doing/to do,will be doing区别No one ___ the building without the permission of the policeA.is leavingB.has leftC.is to leaveD.will be living
问题描述：
be doing/to do,will be doing区别
No one ___ the building without the permission of the police
A.is leaving
B.has left
C.is to leave
D.will be living
答
C
答
选C is leaving代表正在进行的事物,has left代表过去发生的事物,is to leave代表某一时间要发生的事物或者某一客观条件下的事物,will be living 代表在未来某一点确定将要发生的事物,显然句子意思是在“有警察允许”的条件下要发生的事物,所以选择C.