单项选择题
After the passage of a cold front the visibility（）.
A.does not change B.improves rapidly C.improves only slightly D.becomes poor
单项选择题 Advise you（）engines．
单项选择题 Advise（）your fishing gear．
单项选择题 Admiralty Notices to Mariners，containing important information for the mariners and enabling them to keep their charts and books corrected for the latest information，are issued daily and published in（）.
