听力原文：American coast guard officials in Florida say they have returned to Cuba a group

听力原文： American coast guard officials in Florida say they have returned to Cuba a group of would-be migrants who try to make their way to the United States in an unusual vessel, a floating truck. They said one of their planes spotted the Cubans more than half way through their journey, and the coast guard could not believe their eyes when they saw the vessel. The Cubans had attached floats and propellers to a 1951 shabby truck.

What has happened to the Cubans？

A．They set foot in Florida.

B．They were drowned.

C．They were flown to the U.S.

D．They were sent back to Cuba.

请帮忙给出正确答案和分析，谢谢！