一棵树木的高大挺拔代表了森林群落的外貌特征。 [ ]
参考答案:错
Some teachers often give their students too much work to do, ________that they will thus improve
their school grades.
A. hoping
B. to hope
C. hope
D. hoped
电力系统(直接接地系统)发生BC相短路,其边界条件为()。
A.B=C=0,A≠0
B.A=B=C,A=B=C
C.A=B=C,A≠0
D.B=C=0,A=0