What reason would have prompted the designers of the articles of confederation to exclude the role of a president for the nation? a. they did not want to hold elections. b. they were concerned a president could become a tyrant. c. they wanted to create presidents for each state, only. d. they believed that a president would be powerless.

The answer to this question is: B. They were concerned a president could become a tyrant. 
In order to prevent this, articles Confederation enacted the separation of powers which divides the government into three branches.
By doing this, each branch could act as a separate entity that could prevent a single government from being corrupted and untouchable