A towing hook may be released from the（）.

A towing light is（）.

A tug is “in irons” when held in a fixed position by（）

A tug may be in danger of tripping when（）.

A stretch where the channel changes from one side of the river to the other is called a （）.

A towing vessel’s fire detection system may be certified to comply with the Coast Guard’s towing vessel fire protection regulations by（）.

A stage should only be rigged（）.

A slow rise in the barometric pressure forecasts（）.

A swift current occurring in a narrow passage connecting two large bodies of water，which is produced by the continuously changing difference in height of tide at the two ends of the passage，is called a（）.

A tackle is “two blocked” when the blocks are（）.