Munchkin is a popular baby clothing brand. The founder of the company, Ivy, conducts a brainstorming session with her employees every week in order to come up with new ideas to expand the brand. One of her employees suggests that Munchkin should add baby footwear to its collection. In this case, the employee's suggestion is an example of $\_\_\_\_\_.$

a$.$

informal communication

b$.$

downward communication

c$.$

horizontal communication

d$.$

upward communication