This sentence lacks parallel structure; the elements in its list should be formatted in the same way. Here, the third element in the sentence's list, "the door was locked," uses passive voice, describing what was done to the door, not what Alice did. On the other hand, the first two items in the list ("had washed the dishes" and "taken out the trash") each use active voice, describing what Alice did to the dishes and the trash. Changing "the door was locked" from passive to active voice corrects the sentence's error. The corrected sentence reads, "Before Alice left the house, she made sure that she had washed the dishes, taken out the trash, and locked the door."

A sentence should be consistent in its use of verb tense, comparisons, and tone. In the sentence above, "to learn," an infinitive, is being compared to "mastering," a present progressive verb. Things being compared should take on the same grammatical form; that means that "mastering" should be changed to "to master" in order for proper parallel construction to be used. The sentence should read, "It is more difficult to learn to type than it is to master a simple word processing program." "To type" is being compared to "to master"; both are in the infinitive form in this revised case.

This sentence has a problem with parallelism. The items in its list aren't all formatted in the same way: the first two things that we're told Marvin learns to do in his training course are "address customer concerns" and "fill out budget requests," each of these phrases beginning with an infinitive verb. The third thing that Marvin learns to do is "setting up a company account"; in contrast to the previous two infinitive phrases, "setting up a company account" is unnecessarily conjugated to be in the present progressive tense. Since changing the first two items to be in the present progressive tense (as well as the rest of the sentence to make this work grammatically) isn't an option, the answer "and setting up" contains the sentence's error. You could correct the sentence by changing "and setting up" to "and set up," making the corrected sentence, "In his training course, Marvin learned how to address customer concerns, fill out budget requests, and set up a company account."

This sentence has a problem with parallelism. The verbs “communicate” and “solving” should be formatted in the same way, since they are the two things it was "more difficult" for Mary to do. Since only "solving it," and not "communicate," is underlined, "solving it" contains the sentence's error and is the correct answer. The corrected sentence reads, "Although it was easy for Mary to identify the problem, she found it more difficult to communicate with the technical crew and solve it."

This sentence does not have parallel structure between the items in the list. The first three are gerund verbs, but the fourth is a noun. The corrected sentence reads: Lisa insisted that her favorite activities included camping, reading, drinking tea, and hiking.

This sentence has a problem with parallel structure. All of the items in the list should be in the same verb tense, but the third item here is in a different tense. The corrected sentence reads: Until he started his first food service job, Hank had never mopped a floor, scrubbed a wall, or washed dishes.

In this sentence, the format of the two items being compared does not stay parallel. “Drive” is a verb, and “bus” is a noun. The corrected sentence reads: It’s a long drive, but I would much rather drive home than take the bus.

This sentence lacks grammatical parallelism. The phrase “not being so” is clunky, and it doesn’t match with the earlier part “were morally excusable.” The corrected sentence reads: The spies started to empathize with the man they were watching, and suddenly they wondered if their actions were morally excusable or not.

This sentence has a problem with parallelism. The items in the list should be formatted the same. The corrected sentence reads, "She aspired to someday live in Barcelona, learn Spanish, and travel through the country."

All of the items in this poor tired fellow's list of activities need to be in the same form. Yet we find three verbs ("nap," "watch," and "work out") and one adjective ("tired"). Thus, the adjective is the odd one out and needs to be changed (to something like "am always tired").