What is most likely Mr. White's final wish?

Although the account is in good standing at this point in time. is this sentence incomplete or complete?

How can you avoid the problem of groupthink? a. by choosing a group leader to direct the group b. by composing the team of only like-minded individuals c. by encouraging all members to voice their opinions d. by keeping quiet when you disagree with another group member's opinion

Which statement is an historical example that supports her thesis statement?