This is a great sentence and question that tests your knowledge of commas, appositives, introductory phrases. 

Lets first deal with the question: to comma or not to comma. Should there be a comma before Levi Strauss? After Levi Strauss? On either side of Levi Strauss? Or just no comma at all? In order to answer this question, it is important to know what concept is being tested here. It is a question about appositives. 

The real question to ask yourself is whether Levi Strauss is essential to the sentence or not. You could also ask yourself if there is more than one “clothing store owner” in the world. If there is more than one “clothing store owner” in the world, then Levi Strauss becomes essential to the sentence. Levi Strauss is the subject. Levi Strauss cannot be between commas. He is essential (in more ways than one - my wardrobe would be very different had Levi Strauss been non-essential). 

When a name is essential to a clause, it (the name) cannot go between commas. However, if the sentence had read “The founder of Levi Strauss & Co, Levi Strauss, was an important man in the history of fashion” then we would have commas around Levi Strauss. Why? Because he was the only founder. His name is non-essential. By saying the founder of Levi Strauss & Co, we already know that we are talking about Levi Strauss. Got it? If a name is non-essential, we put it between commas.

The next question I am often faced with as a teacher is why is F not correct. Why can’t there be a comma before Levi Strauss. That would put clothing store owner between commas, make it non-essential, and the sentence would read In the late 1800s Levi Strauss patented… This is an important question, and it is important to know here that the comma after “In the late 1800s” is used for something else. It is being used to set off the introductory phrase “In the late 1800s”. That comma is essential. In other words, the real clause starts with “Clothing store owner…”

This brings me to one of my big lessons on English grammar: commas are NOT about pauses. It would SOUND good if one had a comma before Levi Strauss, but commas are not musical objects. They are punctuation marks that have purpose. Their purpose is NOT TO CREATE PAUSES. 

The answer to question 46 can actually be explained later in the sentence when commas are placed around “tiny metal studs”. Why are there commas around “tiny metal studs”? Because they are irrelevant to the sentence! They are simply describing what rivets are. Therefore, if the sentence would have read “In the late 1800s, Levi Strauss, a clothing store owner, patented the practice…” there would have been commas around “a clothing store owner”. Why? Because being a clothing store owner is non-essential! It is simply adding a little more information to the subject of the sentence - Levi Strauss.