单项选择题 Which of the following statements concerning cargo is correct?（）

单项选择题 Before work is commenced（）,the officer responsible should inform the duty en-gineer to ensure that steps are taken to reduce as far as practicable the emission of steam, harmful gases and fumes.

单项选择题 Before wore is commenced（）the officer responsible should ensure that power is shut off and warning notices posted on the bridge and in the machinery spaces.