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Answer to video quiz:
"In principal [incorrect: should be principle, the a noun] the teacher gives students two months' [correct: plural possessive, more than one month] time to master the material, but she knew summer job's [incorrect: no possessive, delete apostrophe] would effect [incorrect: should be affect, a verb] exam scores, so she lay [correct: put or place, transitive] down a series of grammar principles designed to affect [incorrect: should be effect] change more quickly."