[A] blanketing [B] contend [C] encounter [D] environmental [E] exactly

[F] flowing [G] growth [H] naturally [I] options [J] portions

[K] potential [L] relatively [M] significant [N] superficial [O] transported

The spectacular Great Barrier Reef is one of the wonders of the natural world, but it faces numerous threats ranging from climate change to hungry parasitic (寄生的) starfish. There’s now another problem to【C1】_____with after heavy flooding in northeastern Australia created vast plumes of polluted floodwater【C2】_____many parts of the reef.

In the past few weeks,【C3】_____quantities of rain have fallen on Australia’s Queensland state, washing sediment and harmful chemicals into rivers, which are then being【C4】__into the sea. The plumes of dirty water are so large that they can be seen from space. In fact, satellite imagery indicates that the flood run-off (径流) is affecting【C5】_____of the reef located up to 37 miles from the coast.

Scientists say that the polluted run-off—which could include chemicals commonly used in agriculture—has the【C6】_____to kill coral and sea grass in the reef if it persists for long enough. The chemicals in the water have even led to the【C7】__of algae in some areas, creating thick layers of green. Plumes of dirty water are easily broken up by wind and waves. However, the weather has been【C8】_____calm since the floods.

At present, it is not clear【C9】_____how much damage the flood run-off is doing to the reef—but the picture will become clearer soon when the Australian Institute of Marine Science issues its report on the situation. The newest【C10】_____threat couldn’t have come at a worse time for the reef, which in the last few years has been struck by a damaging cyclone and two catastrophic mass coral bleaching events—the worst in recorded history.

【C4】