寄生虫感染的最常见的方式是()
A.经口感染
B.经皮肤感染
C.经胎盘感染
D.自体感染
E.其他感染
参考答案:A
The computer was one of the greatest______ in the 20th century.
A.inventions
B.discoveries
C.findings
D.explorations
污水平均日流量Q=450L/s,则最大日流量为()L/s。
A.520.5
B.620.5
C.656
D.587