Which of the following describes concrete details?

A. words that illustrate an idea

B. exact words taken from a speech or text

C. exact meanings of all the key words in a text

D. specific and observable facts that help with understanding

D. specific and observable facts that help with understanding

The correct answer is D. specific and observable facts that help with understanding.

To determine which option best describes concrete details, let's analyze each option.

A. Words that illustrate an idea: While concrete details do provide a clear picture or understanding, they are not necessarily focused on illustrating an idea. This may be more closely related to figurative language or descriptive language.

B. Exact words taken from a speech or text: This option refers to direct quotations or verbatim passages from a speech or text, which is not specifically related to concrete details.

C. Exact meanings of all the key words in a text: This option pertains to the precise definitions of important terms used in a text, which is not directly linked to concrete details.

D. Specific and observable facts that help with understanding: This option accurately describes concrete details. Concrete details refer to specific and observable facts, details, or information that enhance comprehension and provide a clear picture of a topic or subject.

Therefore, the correct answer is D. specific and observable facts that help with understanding.