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What would MOST LIKELY happen if the Thames Barrier failed?
A) The fish population would decrease.
B) London would be in danger of flooding.
C) There would not be enough drinking water.
D) Ships would not be able to leave the docks.

B. London would be in danger of flooding.

Explanation:

The "Thames Barrier" is a barrier system that is considered a movable one. During high tide, the barrier is opened while during low-tide, it is closed. It started its operations in 1982 and since then, it has been helpful in preventing floods to the majority of places in London (a city in England).

Clearly, if Thames Barrier failed, then London would be in danger of flooding. Much of this flood would come from the rivers and streams that stretches in most areas of Greater London.

So, this explains the answer.