Unsold Goods
(A) Verb (is slowed)
(B) CORRECT
(C) Verb (had piled up); Modifier (with X)
(D) Modifier (with X)
(E) Verb (has slowed)
First glance
Three of the answer choices begin with unsold goods, while two begin with consumer spending. Whenever answer choices move parts of the sentence around, consider Structure and Modifiers.
Issues
(1) Verb: is slowed / has slowed / slowed / had piled
In all of the answer choices except for (C), slow appears as a verb, and each one is in a different tense. When faced with a verb tense split, eliminate any answers in which the verb tense doesn’t match the intended timeline of the sentence.
Before the underline, the sentence states that business were expanding their production, using the past progressive tense. While this happened, the actions in the underlined section happened. Therefore, the underlined section should also be one of the past tenses.
Answer (A) uses the present tense is slowed, and answer (E) uses the present perfect has slowed. Eliminate answers (A) and (E) for faulty tenses.
Answer choice (C), had piled, uses the past perfect tense. This verb tense is used to indicate that one action in the past happened prior to another action but, in this sentence, the two actions occurred at the same time (while). Eliminate answer (C).
(2) Modifier: with X
Answers (A) and (B) use the word "As" to join the two ideas of goods piling up and consumer spending slowing. Answers (C), (D), and (E) use the word with instead.
"As" can be correctly used as a conjunction to join two independent clauses. This is the case in answers (A) and (B).
The lack of a comma before with in answer choice (C) indicates that the modifier will modify a noun. However, with a sharp slowing of consumer spending does not logically modify any of the nearby nouns, such as shelves or unsold goods. Eliminate answer (C).
In answer (D), the modifier is with the piling up of unsold goods. When a with modifier is structured as with the [-ing word] of [noun], the With modifier generally describes the cause of the clause it’s attached to. For instance, the following is correct:
With the slowing of consumer spending, unsold goods piled up on store shelves.
The "With Clause" is the reason for the why the main clause is occuring.
However, in (D), because the piling up of goods did not cause the slowing of spending, the with modifier is used incorrectly in answer (D).
Note: In answer (E), the modifier is with unsold goods piling up on store shelves. When a with modifier is structured as with [noun] [-ing word], there does not need to be a causal relationship between the modifier and its clause. Therefore, the with modifier in answer (E) is acceptable.
The Correct Answer
Correct answer (B) properly clarifies the relationship between goods piling up and consumer spending slowed by using the conjunction as. It also correctly places the action in the past using the verb were piling up.