将4.9克Mg和Fe的混合物在一定量的稀HNO₃溶液中完全溶解（溶液中有Fe²⁺），得到标准状况下气体2.24L（假设全为NO气体），则向反应后的溶液中加入足量的烧碱，在空气中不断搅拌，充分反应后，则生成沉淀的质量有可能是（　　）

A．6g

B．8g

C．10g

D．10.5g

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