Explanation

The last part of the sentence parallels the middle part. The clue to the blank is the rapid development of numerous related processes, so the missing word must mean rapid development or expansion.

Eliminate choice (B) since it is the opposite of what you’re looking for. Choices (C), (D), and (E) seem applicable, but none of these choices stays in the scope of the meaning you need in the blank. Although the daguerreotype was the oldest photographic process, there’s no context for this in the blank and you can eliminate those three choices.

That leaves correct choices (A) and (F), both of which can mean rapid growth and produce equivalent, appropriate sentences.

Hence options A and F are correct!
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Sandy
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