单项选择题 Before entering a fuel tank that has been cleaned, it should be checked with an oxygen indicator and a/an（）.

单项选择题 While loading bulk oil, you notice oil on the water near the bargeWhich of the following actions should you carry out FIRST?（）

单项选择题 Your vessel is taking on fuel oil when a small leak develops in the hose and you have ordered the pumping stoppedBefore resuming pumping，you should（）.