As it is written, the sentence portrays the president as working with the "leader's of his own party," which has an inappropriate use of the possesive form. The sentence must be corrected to make the word a simple plural form by taking out the apostrophe. Therefore, the correct answer choice is "with his political enemies almost as much as leaders of his own party."

In this sentence, "three weeks" is actually a possessive, as the sentence could be rearranged as "[the] worth of three weeks" and mean the same thing. Therefore, "weeks" should be changed into the possessive form "weeks'." As the only answer choice that appropriately makes this change, "roughly three weeks' worth of work" is the correct answer choice.

The word "who's" is a contraction of "who is," not the possessive form of "who," as it is used in this sentence. The correct possessive form of "who" is "whose." As the only choice to use the appropriate word, "officials were still unsure who's bag was left unattended" is the correct answer.

The correct possessive form of men (a plural word) is "men's." There should be no apostrophe used in the word "daughters," as they do not possess anything in this sentence. 

The example sentence contains two apostrophe errors. First, "it's" in this case is a contraction of "it is." "Its" (with no apostrophe) is used to signal the possessive (e.g. "the machine performed its function"). The most correct, and appropriately formal, version of this sentence would use "it is."

The travelers' "plans" are in this case simply plural, so no apostrophe is needed. "Plan's" would only be used to signal that something belonged to the plans.

This sentence contains an apostrophe error: the sentence uses the word "it's" in the second clause in order to show possession. Unlike other words; however, "its (without an apostrophe)" is the correct possessive form of "it". "It's" is a contraction for "it is." The correct answer choice is "The new campus was finally built; its facilities were considered to be the best.

Attaching 's to a last name (such as Roosevelt) makes it possessive, not plural. For that reason, no apostrophe is necessary here and the suffix should be -s without the apostrophe. The initial semicolon was the appropriate punctuation for the sentence. 

Cleveland is a possessor (of "main attractions") in this sentence, and therefore the added possessive "s" should include an apostrophe as well: "Cleveland's." Since there are only two items in the list ("the Rock & Roll Hall of Fame and a Botanical Garden"), no comma is necessary to separate the two. 

"It's" is a contraction, used to stand in for "it is" or "it has." As evidenced by one of the incorrect answer choices, "it is" makes no sense in this sentence - neither, therefore, does "it's." "Its" (without an apostrophe) is the possessive of "it" and the correct word to use in this sentence.

This sentence misuses an apostrophe. Here, there are multiple cars being possessed by multiple individuals. Since the two individuals are listed separately, they most likely do not own the cars together; therefore, an "'s" should come after both of their names in order to show that they individually own their own cars. If they owned the cars together, then a comma would go after only Jill's name. The correct answer is, "Jack's and Jill's cars were both."