The phrase "a shrewd negotiator" is an interrupting phrase, a phrase that has no bearing on the construction of the sentence but provides additional information. All interrupting phrases must be set apart by commas; therefore, the correct answer choice is "The executive, a shrewd negotiator, always."

The phrase "anxious about their grades" is an interrupting phrase, or one that provides extra information, but is not crucial to the structure of the sentence. All interrupting phrases need to be set apart from the rest of the sentence by commas. The only answer choice that does this is "The students, anxious about their grades, were."

The phrase "a respected team leader" is what is known as an interrupting phrase, or a phrase that provides information but is unnecessary for the structure of the sentence. All interrupting phrases must be set apart from the rest of the sentence by commas; therefore, the correct answer is "The athlete, a respected team leader, was."

The comma in the sentence is incorrectly deployed, as it divides a continuous phrase into two parts. The sentence should actually have no commas in it, as the sentence works as a continual phrase. Therefore, the correct answer choice is "The hardest thing for most new pianists to lean is the correct hand position."

The phrase in quotation marks, "What goes around comes around," is the subject of the sentence, but described as an idiom. This means that it needs to be treated as a full sentence, because it is being referred to as a singular whole. To be a complete sentence, a comma needs to be put between its two parts, making ""What goes around, comes around" is an idiom," the correct answer choice.

The use of the comma in the middle of this sentence is completely unnecessary and weirdly divides the sentence into two. No punctuation is needed in this sentence, and the best choice is to remove the comma. Therefore, the correct answer choice is "Making a great deal of money is rarely a path to happiness."

The sentence does not need more commas inserted into it, but fewer. The sole usage in the sentence is a comma splice, or a random insertion of a comma where it should not be. The correct answer choice is "Many former army commanders came out against the plan in newspapers as soon as the story was leaked."

The use of the comma after "circumstances" is incorrect, as the verb "would" connects the conditional phrase to the rest of the sentence. This means no punctuation is necessary, so "Under no circumstances would he let" is the correct answer.

The phrase "about his new job" is vital to the construction of the sentence, as it provides information about the second part of the sentence; therefore, it should not be set apart by commas. The correct answer is "The worst part about his new job."

Inserting a comma between "nothing" and "but" is incorrect, as the sentence is one complete thought, and should not be broken up by a comma. The only thing that needs to be changed is that the comma needs to be removed from the sentence. Therefore, the correct answer choice is "The fourth place finisher at the Olympics receives nothing but the satisfaction of representing his or her country and competing."