钩体感染后的免疫力是
A.免疫力很低
B.获得较强的同型免疫力
C.获得较强的各型交叉免疫力
D.获得带钩端螺旋体免疫力
E.对各型均无免疫力
参考答案：B
—I’m sure Andrew will win the first prize in the final.
—I think so. He _________ for it for months.
A．was preparing
B．is preparing
C．has been preparing
D．had been preparing
Internet上有许多应用，其中主要用来游览网页信息的是 ( )
A．E-mail
B．FTP
C．Telnet
D．WWW
