A:p∧q
B:p∧¬q
C:¬p∧¬q
D:p∨q
读“中东某资源输出示意图”,回答问题.
They found __________ impossible to finish so much work in such a short time.
在观察人的口腔上皮细胞的实验中,以下操作错误的是( )