A concrete statement can be considered as a 'solid' statement. This means that the sentence must contain hard facts to manifest the credibility of the statement. As much as possible, you give specific examples and provide evidence for this. From the choices, the answer would be D.
I believe the answer is tense
The most crucial to a reader's understanding of an expository text would be how effective the text is written to convey a clear and concise idea to the reader. It should be able to penetrate a reader's comprehension well and establish a clear way to get the point across.
The answer is d because he was a activist who fought for African american rights