This sentence does not contain a comma where necessary. The words "sleek" and "modern" are coordinate adjectives: adjectives that modify the same noun separately, but are not separated with a conjunction. Coordinate adjectives need to be separated with a comma. The correct answer choice is, "The sleek, modern building was a marvel."

This sentence contains a comma where one is not necessary. While the words "great" and "courageous" are coordinate adjectives, and, as such, should be separated by a comma after the word "great," there is no need whatsoever for a comma after the word "courageous." The second comma should be omitted. The correct choice is, "The statue of the great, courageous hero stood."

This sentence does not contain a comma where necessary. The phrase "which the company ordered is an example of a relative clause, which gives more information about its antecedent: equipment. Any such phrase that occurs in the middle of a sentence must be introduced and completed with a comma. The correct answer choice is, "equipment, which the company ordered, seemed to have."

This sentence misuses a comma. Commas are not used to separate prepositional phrases from a sentence unless the phrase acts as a parenthetical expression (a phrase that explains more about a particular word in the sentence). The comma should be omitted. No additional punctuation is necessary (colons do not divide up a clause). The correct choice is, "She moved to the mountains in order."

This sentence misuses the last comma present. "Clara mentioned her new promotion" is a simple sentence and does not need any sort of punctuation. The previous phrase, however (While on the phone with her parents), is an example of an introductory phrase that explains information necessary to the context of the sentence, but exists outside of the main clause, grammatically. These types of phrases must be followed by a comma in order to separate them from the rest of the sentence. The correct choice is, "her parents, Clara mentioned her new promotion."

This sentence is listing several items.  To separate independent objects in a list, we need to use a comma.  Here, we are marking the associated words in the sentence.  Therefore, we need a comma after 'bananas' and 'oranges'.  We do not need one after strawberries because that is leading to the conclusion of the sentence. 

This sentence needs a comma to separate the first contradictory statement with the second description of Venus.  After turnaround words like 'although', a comma is always necessary.  However, the comma has to come at the end of the completed clause, which comes after the word 'sky'.  No comma is necessary between 'winds' and 'and' because that part of the sentence is neither listing three or more things or containing two complete clauses.  

To look for sentence punctuation errors, we must look to the left and right of the underlined portion. To the left of 'because', we have a complete sentence. To the right, it is not a complete sentence. All of the options, however, still have 'because' connecting the two clauses. Therefore, the best version is as written in the original. 

The original sentence is the best version of the complete sentence. The comma punctuation here is being used to separate the noun ("Sally") from a describing characteristic. The appositive clause ("she is a baker") is being offset from the rest of the sentence to rename a proper noun with the use of two commas. 

In this sentence we not only are introducing a list, but the list is or ordered pairs. Therefore, we cannot just separate the pairs with more commas because that takes away the meaning of the sentence. In this case, since the list includes complex items, semicolons are actually the correct option to separate these items. We also need the colon to separate the list of ordered pairs, as the sentence was originally written.