脊髓灰质炎、甲型肝炎等病毒的病毒体结构组成是
A．核酸和刺突
B．衣壳和包膜
C．基质蛋白和衣壳
D．核酸和衣壳
E．核酸和包膜
参考答案：D
Our teacher asked us to ________ exercise books after finishing our exercises. [ ]
A. hand down
B. hand in
C. hand out
D. hand over
Education is not an end, but a means to an end. ______, we do not educate children only for the aim of educating them.
A．In the end
B．After all
C．In other words
D．In the meantime
