航行值班中，了望人员必须全神贯注地保持正规了望，不得从事或被分派给会影响了望的其他任务。
参考答案：对
—Here are two apples, but you can only eat either of them.
—But can I have some bananas, Mum?
A．another one.
B．one of them.
C．neither this one nor that one.
D．both of them.
一般情况下，国家发展改革委员会在收到备案材料之日起( )个工作日内出具备案证明。
A．5B．7C．10D．15
