Explanation
Correct answer: B.
Choice B is the best answer. The convention being tested is punctuation between a supplementary element and a main clause. This choice correctly uses a comma to mark the boundary between the supplementary phrase (“While...1947”), which indicates when the action occurred, and the main clause (“Howe had a handheld camera operator wear roller skates”).
Why the other choices are wrong
Choice A
Choice A is incorrect because a comma paired with the conjunction “and” can’t be used in this way to mark the boundary between the supplementary element (“While…1947”) and the main clause (“Howe…skates”).
Choice C
Choice C is incorrect because the conjunction “and” can’t be used in this way to join the supplementary element (“While…1947”) and the main clause (“Howe…skates”).
Choice D
Choice D is incorrect because it fails to mark the boundary between the supplementary element and the main clause with appropriate punctuation.