Open . . . . . . . . book at . . . . . . . . page 20 and read . . . . . . . . text.

The correct answer is: A. no article, the, the

The article "the" is used before a specific noun. In this case, the noun is "book". The book is specific because it is being referred to by its page number, 20.

The article "a" is used before an indefinite noun. In this case, the noun is "text". The text is indefinite because it is not being referred to by a specific name or title.

Therefore, the correct answer is: A. no article, the, the.

Here is a brief explanation of each option:

• Option A: no article, the, the. This is the correct answer because the book is specific and the text is indefinite.
• Option B: the, no article, the. This is incorrect because the article "the" is used before both the book and the text.
• Option C: no article, no article, the. This is incorrect because the article "the" is used before the text.
• Option D: the, no article, a. This is incorrect because the article "a" is used before the text.