This sentence misuses a comma. Commas can only be used to combine independent clauses when a conjunction is present. This is not the case. When a conjunction is not present, the most appropriate punctuation in this case is a semicolon. Note that a colon would not be appropriate since the second clause, while related, does not actually explain anything about the act of collecting the stamps. The correct choice is "had been collecting stamps for years; her collection is now filled."

This sentence misuses a comma. Commas are generally used to separate clauses, but a prepositional phrase (here: "in hope of finding a rare book") does not start a new clause. Commas generally do not appear before prepositions. The correct chocie is "the library in hope of finding a rare book." The other choices contain dangling prepositions or the same error in using the comma (among others). 

This sentence does not contain a comma where one is necessary. Since the phrase "It is always important to stretch before running" is a direct quote, a comma should appear after the word "said." A colon could also be used (though, commas are more appropriate), but not with single quotation marks, since this is not a quote within a quote.

This sentence does not contain a comma where necessary. The phrase "While he completed the test" is an example of an introductory phrase, explaining information necessary to the context of the sentence, but outside of the main sentence, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. The correct answer choice is, "While he completed the test, he forgot."

This sentence does not contain commas where they are necessary. The phrase "such as sleeping and eating well" is a paranthetical expression: a phrase that explains more about a particular word or phrase in the sentence, but is not introduced by a relative pronoun. These phrases must be introduced and completed with a comma in order to separate them from the main clause of the sentence. The correct answer choice is, " things, such as sleeping and eating well, can have a huge impact."

This sentence does not contain a comma where one is necessary. The phrase "After much practice" is an example of an introductory phrase, explaining information necessary to the context of the sentence, but outside of the main sentence, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. The correct answer choice is, "After much practice, Tammy's tennis game."

This sentence does not contain a comma where one is necessary. Since this is a direct quote, a comma should appear after the word "said." Note that Double quotations must be used (single quotations are only used when a quote appears within an already existing quote). The correct choice is, "Michael Dell said, "You don't have to be a genius or a visionary or even a college graduate to be successful."

This sentence does not contain a comma where one is necessary. The phrase "Because of her promotion" is an example of an introductory phrase, explaining information necessary to the context of the sentence, but outside of the main sentence, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. The correct answer choice is, "Because of her promotion, Heidi was moving."

This sentence does not contain a comma where necessary. The phrase "Surprisingly" is an example of an introductory phrase, explaining information necessary to the context of the sentence, but outside of the main sentence, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. The correct answer choice is, "Surprisingly, he managed to win the contest."

This sentence contains a comma where one is not necessary. Commas are generally used to separate clauses, but the word "ever" is in the same clause as "written," and they are not coordinate adjectives. The comma should be omitted. Note that no additional punctuation is necessary because prepositional phrases do not start new clauses, which is necessary for the use of any of the punctuation present in the above choices (commas, colons). The correct choice is, "the longest books ever written in history."