Read and choose the correct word in the blank

Read and choose the correct word in the blank. 
Not many people have seen an otter. These animals live ______ rivers and make their homes from small pieces of wood. They usually come ________ of their homes at night. Otters are very good in the water and can swim at more than 10 kilometers _______ hour. They have thick brown hair and this _______ them warm in the water. An otter can close _______ ears and nose. This means otters can stay underwater _______ several minutes.

Twenty years ago, there were _______otters in Great Britain. The water in the rivers was so dirty that many fish and insects died and the otters couldn't find anything to eat. But today there is lots of food for them _______ the rivers are clean again.