This sentence contains a dangling preposition. A preposition should never end a sentence in English. "about his new position, but he did not know to whom he should talk" is the correct choice, as it fixes this issue. The other choices contain punctuation errors (Note: a comma should be used before "but" because it is joining two independent clauses) or change the action to passive voice unnecessarily.

This sentence contains a dangling preposition. You should never end a sentence with a preposition in standard English. Additionally, "yet" cannot come at the end of the sentence either, since it is a conjunction. The only choice that fixes this issue is, "Though Harun has broken many records, he has not yet broken the record he wants to break."

This sentence contains a dangling preposition. Prepositions should never end a sentence in standard English. The only sentence which fixes this issue and makes sense is "monitored to which clients the employees talked."

This sentence contains a dangling preposition. The only choice that corrects this error properly is, "the message did not reveal who sent it." Note that the choice that states "from whom it was sent" is in the passive voice (correct choices will always be in the active voice), so it cannot be the correct answer.

This sentence contains a dangling preposition. Prepositions should never appear at the end of a sentence. Instead of saying "which department he should deliver his work to," it should be "to which department he should deliver his work." The correct choice is, "Lamar was unsure to which department he should deliver his work."

This sentence contains a dangling preposition; a preposition should never end a clause in standard English. In actuality, there is no need for the word "of" whatsoever, and all that is needed is to omit it. The correct choice is, "what the next invention would be."

This sentence contains a dangling preposition. Prepositions should never end a clause. The sentence needs to be reworded. The correct choice is "She wondered who was in the painting" as the other choices either have the dangling preposition or pronoun errors.

The most idiomatic use of prepositions is "Her inquiry into the petroleum cartels of Brazil." The phrase "inquiry about" is unidiomatic. And many of the adjustments to the preposition preceding Brazil are seemingly trivial. It is important in this case to examine each choice carefully and consider both prepositions and the particular context of their use.

The placement of "both" in this sentence makes the underlined phrase confusing and awkward. By placing the word "both" nearer to the two things it joins together, "current combat tasks and future endeavors," makes the meaning of the sentence much more clear. The only answer choice which correctly makes this change is "which helps them with both current combat tasks and future endeavors."

The sentence is not technically gramatically correct as it is written, but it is awkwardly worded and unnecessarily long. The sentence is best served by being shortened to a more direct statement that conveys the same meaning. The answer choice that best does this kind of streamlining is "who knew he would always puthis family first."