to create, test, and improve products to manage the manufacturing of products to persuade customers to buy the products to label, package, and send products to retail stores
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which of the following is the most important function of the research and development department of a large corporation?
Possibilities:
- to create, test, and improve products
- to manage the manufacturing of products
- to persuade customers to buy the products
- to label, package, and send products to retail stores

to create, test, and improve products