问题
单项选择题
According to the passage, efficiency of e-mail is threatened by ______
A．heavy e-mail traffic
B．fraudulent e-mail messages
C．large volume of messages
D．increasing amount of unwanted e-mail
答案
参考答案：D
解析：[分析] 细节题型。 见第二段第一句：The convenience and efficiency of electronic mail are threatened by _______ unsolicited commercial electronic mail．从第三段得知unsolicited commercial electronic mail指的是unwanted messages；因此选项D为答案。