Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 34 to 40.

Back in 1853, at the age of 24, Levi Strauss opened a west coast branch of his brother's dry goods business in New York. Over the next twenty years, he built his business into a lucrative operation.

One of Levi's customers was a tailor by the name of Jacob Davis. Originally from Latvia, Jacob lived in Reno, Nevada, and regularly purchased bolts of cloth from Levi Strauss & Co. Among Jacob's customers was a man who kept ripping the pockets on the pants that Jacob made for him. Jacob tried to find a way to strengthen his customer's pants when, one day, it finally occurred to him. He decided to put metal rivets on the pocket corners and at the base of the button fly. It worked and the pants became an instant success.

Jacob knew he had discovered something new and worried that someone might steal his idea. That's why he decided to apply for a patent, but he didn't have the $68 that was required for the paperwork. So, he turned to Levi Strauss. He wrote him a letter suggesting that they hold the patent together. Being the businessman that he was, Strauss agreed immediately seeing the potential for this new product. So, on May 20, 1873, the two men received patent number 139,121 from the US Patent and Trademark Office and went into business together. That was the day blue jeans were born. Who would have thought back then that denim, thread and a little metal would become the most popular clothing product in the world and it's all thanks to two men - Levi Strauss and Jacob Davis.

Why did Jacob put metal rivets on the pants he made?