The word "part" must be pluralized in order to reflect the use of the word "all." We should therefore change the phrase to "all of the different parts."

"All film directors" is a plural noun in which all film directors are described as a unified group. The example sentence incorrectly shifts to a singular pronoun ("his") later in the sentence. In order for a singular pronoun to be correct in this situation, the sentence would have to be begin "Any film director" and the preferred pronoun form is gender neutral: "Any film director must be thoughtful in his or her use of light and shadow." The use of "all" means that the film directors must be treated as a unified group of many people. The correct version of the sentence reads, "All film directors must be thoughtful in their use of light and shadow."

The example sentence makes a modifier error. In order for the sentence to be correct, the "time" must either be treated as a unified, grammatically singular block of time (in which case "all this time" is the correct phrasing), or treated as multiple occurrences (grammatically plural) in which case "all these times" is correct. In either case, the modifier and the word modified must agree in number. Since it is the only one of these options that is included without additional errors, the correct response reads, "Even after all this time, I still do not know how to swim." 

The key issue with the underlined phrase is the simultaneous use of "an" and the plural form "studies." Either the singular "an" or the plural "studies" needs to be changed to make the forms match. "An objective study" is the correct answer choice.

The major issue here is not only the misplaced modifier "civil engineers" but also modifier agreement. Note that using the plural "civil engineers" is inappropriate. The correct placement of the modifier uses the phrase to modify Marcus. To convey Marcus' profession (singular), one must adjust the modifier to agree with the singular noun. The incorrect answer choices fail to resolve both of these issues and result in awkward syntax or modifier placement errors.

"Just one" is singular; therefore, the verb must be conjugated to agree with a singular subject. Entrepreneurs also must change to the singular form. The second part of the sentence is correct in the question. Semicolons can link two related, independent clauses, with or without the use of a conjunction like "however" or "therefore."

The use of both "favoring" and "buying" in the opening phrase is awkward and ruins the parallelism between the suits and the shoes. Tying the two items to the same verb streamlines the phrase and makes the sentence more gramatically correct. " Favoring handmade suits and Italian leather shoes" is the only answer choice that makes the appropriate correction to the sentence.

In this question, the nouns "both" and "triplets" disagree. Triplets would suggest three things, while "both" only applies to differentiating between two options. Therefore "both" should be replaced, perhaps with a word like "all."

In this sentence, "all students" establishes the subject as plural. Therefore the "rich, famous author" must be changed to be plural: "All students in my program wish to become rich, famous authors." 

Because the writer is included in "all students in my program," the most correct version of this sentence would include the author in the assertion that "none of us will."

Because the subject of the sentence is the plural “students,” we have to assume that each student would have his or her own pencil and drawing pad. Therefore, the correct sentence has “pencils” and “drawing pads.” Also, “had sharpened” is more concise and correct than “were having sharpened” or “were having sharpening.”