单项选择题
63 ______ the Atlantic Ocean crosses the equator, the tide winds cause a flow of water to the west.
单项选择题 It was recommended that passengers ______ smoke during the flight.
单项选择题 It was not until midnight ______ the snowcapped peak.
单项选择题 ______ is often the case with a new idea, much preliminary activity and optimistic discussion produced no concrete proposals.
