凡登白试验间接反应阳性，尿胆红素阴性，尿胆素原增加（）

A.溶血性黄疸

B.阻塞性黄疸

C.肝细胞性黄疸

D.后天性卟啉症

E.多发性骨髓瘤

The major problem with E-mail is that it is (71) easy to use that people can become (72) with messages (73) they can possibly answer in a day. In addition, mail boxes require some management to (74) messages or archive those that might be required later. Senders don’t always know about your E-mail backlog and often send (75) messages.

A．too

B．so

C．very

D．much