Commas, gramatically speaking, should never be used before or after the word "that." The correct sentence would have: "James finally saw the movie that his friends . . ."

"Had recommended" could be changed to "recommended", for the sake of simplicity, but the comma error is more flagrant.

The sentence consists of two independent clauses ("Joey will reluctantly eat broccoli and spinach" and "his favorite green vegetables are peas and green beans") joined by a coordinating conjunction, "but." (Other coordinating conjunctions can include "and," "or," "nor," "yet," "so," and "for.") When two independent clauses are joined by a coordinating conjunction, a comma is required after the first clause immediately before the conjunction. The corrected sentence would read, "Joey will reluctantly eat broccoli and spinach, but his favorite green vegetables are peas and green beans."

“While I would love to go to the beach with you” is a dependent clause, which means that if it is removed from the sentence, the rest of the sentence (“I have to study instead”) will still be a complete sentence. Because commas are always used to separate a dependent clause from an independent clause when the dependent clause precedes the independent clause, a comma must appear between “with you” and “I have.”

“Wherever they go” is a dependent clause, so it must be separated from the rest of the sentence by a comma. However, commas generally don’t appear before or after the word “that,” so no comma is necessary there. (Specifically, commas are not generally needed to separate dependent clauses from independent clauses when the dependent clause follows the independent clause.)

“Being a strong student” is a modifier that describes “Chris,” so a comma is needed to separate the two. The three items in the list are properly punctuated with commas, and since "classmates" is plural, the correct possessive is "classmates’."

Because “Here’s the situation” is an independent clause introducing another independent clause, a colon is the correct punctuation mark to use to separate them. A comma is required after “adults,” though, since it’s an item in a list.

The placement of the comma in this sentence between "then" and "a" is incorrect. The comma should instead appear between "vacation" and "but" in order to correctly connect the compound sentence's two independent clauses using a comma followed by a conjunction.

The comma between "loudly" and "when" is unnecessary, creating and punctuation error in the sentence.

The sentence requires a comma after "swimmer" in order to correctly join its dependent and independent clauses ("Although Danny was not the best swimmer" and "his friends always said he threw the best pool parties"). 

The sentence consists of two separate clauses ("While I don't agree with your opinion about how life on Earth began" and "I do respect your right to believe it"); therefore, the sentence requires a comma after "began" to properly separate the clauses.