单项选择题
Clouds with the prefix “nimbo” in their name（）.
A.are sheet or layer clouds B.have undergone great vertical development C.are middle or high altitude clouds D.are rain clouds
单项选择题 Clouds form（）.
单项选择题 Clean air standards referred to as “Grade D” apply to compressed air for use in（）.
单项选择题 Class I and II private aids to navigation in or along navigable waters of the United States are listed in the（）.
