Which of the following is a complex sentence?

A complete sentence must have a subject and a predicate that expresses a complete thought. Option B, "I walked all three dogs around the park this morning," is a complete sentence because it has a subject ("I") and a predicate ("walked all three dogs around the park this morning") that expresses a complete thought.

A dangling modifier is a phrase or clause that does not logically modify any word in the sentence. Example: "My brother had an old truck that sat by the garage that needed paint." The phrase "that needed paint" is a dangling modifier because it does not clearly modify any word in the sentence.

It is unclear whether it is the truck or the garage needed paint.

Option B is the correct sentence, which reads "The building's height was exceeded by its width." This sentence employs standard English spelling, where "exceeded" is spelled correctly, and the apostrophe in "it's" is incorrect, as it should be "its" without an apostrophe.

This sentence presents a specific statistic that may not be common knowledge and is not the author's original idea, so it requires a citation to give credit to the source of this information. A citation is needed to show where this statistic came from, who conducted the study, and when it was conducted. Therefore, option C is the correct answer.

The ureter is a large tube that carries urine from the kidneys to the bladder. The other options are small (microscopic) parts of the kidney that help filter blood.

The language convention violated in the sentence is pronoun-antecedent agreement. The pronoun "you" does not agree in number with its antecedent "a person." It should either be "he or she" or "they" to agree with the singular or plural antecedent.

Option C is most likely to be found in an email from a professor to her biology students at a college because it contains specific information related to the class schedule and activities. It mentions the research groups from a specific class meeting time, and gives a location where they should meet, which suggests it is a message intended for students in that class. Options A, B, and D are more likely to be found in casual conversations or in other types of messages not directly related to the biology class.

In the given sentence, "the class" is a singular noun and requires a singular possessive pronoun. "Its" is the correct form of the possessive pronoun "it" to use with a singular noun, as opposed to "it's," which is a contraction of "it is" and would not be appropriate in this context. "They're" is a contraction of "they are" and would not be appropriate because "class" is singular, not plural.

According to the rules of capitalization, the first letter of a sentence and proper nouns should be capitalized. In option D, "Rocky Mountains" is a proper noun and it is capitalized correctly. Geography is also a proper noun identifying a subject.

In option A, "College" should not be capitalized as it is a common noun.

In option B, it is partly correct however"Western" should be capitalized as it is a proper adjective referring to a specific region.

In option C, "A1 Plumbing Board of Directors" is capitalized correctly, but "range" should not be capitalized as it is a common noun.

Therefore, option D is the correct answer.

This sentence is spelled correctly. The other choices have mistakes: "hear" instead of "here," "price" instead of "prize," and "harestyles" instead of "hairstyles."