Where are the _______?( )
A:a potato
B:potato
C:potatoes
A. Let me see. I think it's a toilet for a pet(宠物).
B. Yes. I do. I like studying them.
C. Do you know anything about the public signs?
D. OK. What does that sign on the door mean?
在用显微镜观察人的口腔上皮细胞的实验中,下列说法正确的是( )
观沧海
东临碣石,以观沧海。
水何澹澹,山岛竦峙。
树木丛生,百草丰茂。
秋风萧瑟,洪波涌起。
日月之行,若出其中;
星汉灿烂,若出其里。
幸甚至哉,歌以咏志。
本诗表达了作者怎样的情感?