问题详情：
From April 1, 2009, 3G mobile phones ______ in 8 main cities in China ________of what is going on all over the world faster and more conveniently..
A. are used; to keep informed B. have come into use; to keep people informed
C. come into use; keeping informed D. have been in use; informed
【回答】
B知识点：其他
题型：选择题
