Choose the correct variant. The lake is badly _______.

The correct answer is 'polluted'. Here's why: * 'Badly' is an adverb that modifies a verb or adjective. In this case, it needs to modify the adjective that describes the state of the lake. * 'Polluted' is the past participle of the verb 'to pollute', and it functions as an adjective here, describing the lake. Therefore, the complete and correct sentence is: 'The lake is badly polluted.' Correct answer: polluted