Brainstorming is only effective when done a. in groups b. by yourself c. in a respectful atmosphere d. in a limited amount of time

C.

Explanation:

Brainstorming is the process of group discussion in a free-thinking or a respectful atmosphere. In this process participants are encouraged to speak aloud their ideas and thoughts, without any restrain. These thoughts can be foolish, or vague, or strange.

Brainstorming will be more effective when done in a respectful environment.

It can be made more effective in many other ways such as setting a time-limit by the facilitator, all ideas related with the topic are allowed to be shared no matter how naive may be the idea, criticism or judgement should be avoided in a brainstorming session and letting one person speak at a time.