Answer:
D. working with cells, working with proteins, and working with genes
Explanation:
Biotechnology is referred to as the application of genetic principles on living organisms in order to make useful products. Biotechnologist aims at studying the genetic composition of certain cells and manipulating it to make useful products.
According to this question, working with cells, working with proteins, and working with genes are included as tools of biotechnology when using living cells and their components in different ways.