蛔虫病的主要感染途径是（）
A.皮肤接触
B.经口吞入虫卵
C.经呼吸道
D.经中间宿主传播
E.以上都不是
参考答案：B
— He _____ to Beijing ten times in 1999.
— So he must have covered _____ of it. [ ]
A. went; much
B. had; a lot
C. was going; some
D. had gone; many
示波器X通道的技术性能有哪些？
