The correct answer is a thought-provoking question.
Explanation: A thought-provoking question is an effective technique for engaging readers in an explanatory text because it encourages them to think critically about the topic being discussed. By posing a question that sparks curiosity or prompts reflection, the writer can draw readers in and make them more invested in the content that follows. This technique can create a sense of anticipation and motivate readers to seek answers, thus enhancing their engagement with the text.
In contrast, the other options do not serve the same purpose in an introduction:
- A diagram may be useful for clarification or illustration but does not engage readers in the same way right from the beginning.
- A concluding statement typically summarizes the main points and is found at the end of a text, which does not engage readers at the start.
- A topic sentence introduces a main idea but may not spark curiosity or engagement in the same manner as a thought-provoking question would.
Thus, among the given options, a thought-provoking question is the most effective technique for engaging readers in an explanatory text's introduction.