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Verbal·Standard English Conventions·Boundaries

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Polymers used in industrial applications are weakened by environmental stress, mechanical fatigue, and unexpected damage. However, new types of polymers have been engineered to repair __________ aided by embedded microcapsules, such materials begin to self-heal.

Which choice completes the text so that it conforms to the conventions of Standard English?

A

themselves, upon fracture,

B

themselves—upon fracture—

C

themselves. Upon fracture,

D

themselves upon fracture,