There are no errors in this sentence. A comma is necessary before "even," as the phrase "even though he thought it was boring" is a dependent clause. Dependent clauses should be separated from the main clause with a comma. Using a semicolon would not be appropriate since semicolons are used to join two independent clauses without a conjunction, and a colon should not be used because the second clause does not explain anything about or within the first clause.

This sentence contains no errors. The phrase "a Spanish painter" needs to be offset in commas because it is a parenthetical expression. Furthermore, "Spanish" should be capitalized because the word refers to a nationality.

There are no errors in this sentence. Note here that "because" does not require a comma before or after it because it comes in the middle of a clause. "Usually" is correctly framed in the adverbial form as the word it is modifying is the verb "was."

There are no errors in this sentence. The sentence joins two related independent clauses without the use of a conjunction; therefore, a semicolon is the most appropriate punctuation here. The use of "although" is inappropriate since the sentence shows a cause and effect, and not conflicting statements. The best choice is, "The company was well known for its benefits; employees had access to free meals, transportation, and great healthcare."

There are no errors in this sentence. Note the sentence joins two independent clauses with the coordinating conjunction "but," so a comma must appear before the conjunction. Furthermore, using the word "its" in place of "the phone's" is not appropriate here, because it makes the sentence more ambiguous ("its" could then technically mean that either the phone or IT department has a lack of security features, which is untrue to the meaning in this sentence). 

There are no errors in this sentence. The sentence joins two independent clauses without the use of a coordinate conjunction, so there should be a semicolon before the word "she." Furthermore, a comma is inappropriate in this place because you would need a conjunction in addition to the comma, which is absent here. A colon is also incorrect here because the second clause does not explain anything in or about the first clause, but adds more information about something not previously mentioned. The other sentences contain errors in verb-noun agreement (e.g. "Her hobby were collecting...") and tense shifts (e.g. "Her hobby were collecting...she even sets..."). The correct answer choice is: "Her hobby was collecting models of various types of vehicles; she even set aside a room just for the models."

The above sentence is correct. The sentence joins two independent clauses together with the use of the coordinate conjunction "but," so there should be comma before this word. Furthermore, the word "whether" is appropriate; it is not necessary to use the common phrases "whether or not" or "whether...or," and, in fact, "whether...or" would be completely out of place here because there is no additional option after the "whether." The correct choice is: "Chelsea wanted to visit her family over the weekend, but she was unsure whether she would be able to finish her work if she did."

Note: In the choice that omits "she" after the word "but," the comma cannot be used because this omission makes the last clause a dependent one, since it lacks a subject. While it is obvious that the "she" is implied, grammatically, the "she" needs to literally be in the sentence in order for it to function as an independent clause.

This sentence contains no errors. The phrase "From time to time" 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, "From time to time, Juan liked to look at his trophies."

This sentence contains no errors. The word "because" does not take a comma before it, even though it joins two independent clauses. "Its" is the correct possessive form of the word "it," and "their" would not be appropriate because it describes "company," which is singular. The usage of "it" instead of reiterating "the company" is also not vague because there is only one singular noun (the company) to which it could possibly refer. The correct answer is, "The company's new acquisition surprised everyone because they were not able to see how it would help to its core business."

This sentence contains no errors. It joins two independent clauses with the use of the coordinate conjunction "yet," which properly has a comma preceding it. The correct choice is, "She had many hobbies, yet she rarely had the time to do them."