Here's a problem to solve: Which of the following is the most important function of the research and development department of a large corporation?

Among the 4 following options, which is the correct answer?

- A: to create, test, and improve products
 
- B: to manage the manufacturing of products
 
- C: to persuade customers to buy the products
 
- D: to label, package, and send products to retail stores
 