Remember our parallelism challenge cliffhanger?  You’ve discussed your thoughts in the comments section; now let’s go over this question in detail.

The recent decline in bus commuter ridership has left the system underfunded, to cause the number of buses running during peak times to drop, and prompts concerns that further service cuts may lead to the collapse of the city’s entire public transportation system.

1. a. to cause the number of buses running during peak times to drop, and prompts
2. b. causing the number of buses running during peak times to drop and prompting
3. c. to cause reductions in the number of buses running during peak times and prompt
4. d. to cause the number of buses running during peak times to be reduced, and prompted
5. e. causing a reduction in the number of buses running during peak times and prompting

There are a couple of ways to make this parallel.  First, you could look at the three main verbs as a list: “left the system underfunded” is the first one, and since it’s not underlined, it’s the one we have to match.  In order to do that, we would need to put the other two verbs—cause and prompt—in the past tense.  That list would be “…has left the system underfunded, caused the number of buses… and prompted concerns…” But a quick scan of the answer choices shows us that none of them begin with “caused,” so we have to try a different option: we look at the underlined portion as the beginning of a modifying phrase that describes the results of the system being underfunded.  In order to introduce that kind of phrase, we need the gerund “causing,” which leaves us with only choices ‘b’ and ‘e’ to evaluate.

That’s a tougher issue, and one that isn’t governed by parallel structure.  This comes down to word choice: “causing the number… to drop” doesn’t clearly show that the number was reduced in response to an underfunded system.  “Causing a reduction…” tells us that the underfunded system resulted in the number of buses being reduced, with the implication that the reduction was a conscious decision, rather than an unforeseen consequence.

An issue that frequently comes into play with parallel structure is verb tense, as we saw in the previous question.  Let’s look at a verb tense question; note your answers and reasoning in the comments section, and we’ll examine this question in depth in an upcoming article.

The benefits of the teacher’s new academic achievement reward program are evident in the student’s grades, which increased by a full point this semester after it fell last semester.

1. a. which increased by a full point this semester after it fell
2. b. which had increased by a full point this semester after it had fallen
3. c. which have increased by a full point this semester after falling
4. d. with an increase of a full point this semester after falling
5. e. with an increase of a full point this semester after having fallen