What is the main idea of this reading?

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

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.

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

Without action the impacts of climate change threaten to catastrophically damage our world.

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.

Each ethnic group has its own cultural identities, thus, the Vietnamese culture has both            and unity.

For (A) such a demanding job, you (B) will need (C) qualifications, soft skills, (D) having full commitment.

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

She helped us a lot with our project. We couldn't continue without her.

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

A new TV show has sparked                by showing the positive side of dropping out of college.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following sentences.

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.

The sun is a powerful energy source, and this energy source can be harnessed by installing solar.

Why are the forests in Alaska being destroyed?