The use of "have," a past-tense helping (auxiliary) verb, makes the verb in the sentence past-tense and perfect. However, "sing," a present-tense verb, completes the signaled past perfect form incorrectly and introduces confusion about the sentence's tense. While we could change the verbs in the sentence in many ways to correct the error, only "always sing" is underlined. This means that we can't alter "have," so we need to change "sing" to "sung" to create a correct past perfect verb ("have . . . sung"). The answer choices "always sing" and "sing always" don't correct the sentence's error. "Always sang" may look potentially correct, but "to sing" is an irregular verb in which "sang" is the past tense and "sung" is used in the perfect tense (Example: "She sang the song yesterday, after she had sung the duet."). "Always sang" can't be the correct answer, then, because it incorrectly constructs the past perfect tense. While "always sung" and "sung always" may each look like a potentially correct answer, "sung always" introduces an awkward word order that "always sung" avoids, so "always sung" is the correct answer, making the corrected sentence, "We have always sung anthems that celebrate our nation."

The sentence describes what Transcendentalists did "In the nineteenth century." This indicates the underlined portion of the sentence needs to make use of the past tense, because that part of the sentence is describing the actions that took place "In the nineteenth century." Only "seeking" needs to be changed, as the form "to find" is an infinitive, and does not change regardless of the tense of the verb that precedes it. "Sought to find" is the correct answer choice.

We know that the proper tense to describe an event that happened "over the course of past year" is the present perfect, which narrows down potentially correct answer choices to either "have increased the company's profitability" or "has increased the company's profitability." 

Since the subject of the increasing event is "wave," not "advances," we should go with the answer choice that uses the singular verb—"has increased the company's profitability."

The underlined portion describes what happened "Previously," which indicates the verb has to be in a tense showing what happened before. The correct answer must be in the past tense, and only "refused to run" has the correct tense among the answers.

The original sentence uses the pluperfect verb form ("had gone to the gas station") erroneously because the event of going to the gas station happened after Miguel left the store.

One can never say “If I would have done”. One can only say “If I had done”, which is called the past perfect verb form.

The word "thinking" is acting like a participle in the original sentence, making the first clause lack a verb. Changing "Many parents mistakenly thinking" to "Many parents mistakenly think" corrects the sentence's error.

The original statement uses the wrong verb tense for the verb "take"; it should be "took". The correct answer is also more concise than the original.

The original statement erroneously uses the past progressive verb tense "were believing" instead of "believed." The correct answer is also less awkward and more concise than the original.

The use of the verb "learn" is essentially as a modifier of the students "shock." This means that "learning" must be turned into a form that will describe why the students were "shocked." "Were shocked to learn," using an infinitive form, is the best choice among the answers.