The lessons provided by Duolingo are designed to increase in difficulty as the user              .

What should be the best title for the passage?

The man            his car outside hasn't come back for it yet.

Mark the letter A, B, C, or D on your answer sheet to indicate the word whose underlined part differs from the other three in pronunciation in each of the following questions.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.

Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the underlined word(s) in each of the following questions.

Many herbicides and pesticides take a long time to degrade and build up in the soils or throughout the food chain.

What is the writer's main aim in writing the text?