What is the main role of campaign influence?

Answer options:

A.To track the influence of multiple campaigns against an opportunity
B.To track the influence of a single campaign against an opportunity
C.To track the campaign owners influence
D.To track the campaigns influence against other campaigns

Correct Answer: A 
You can configure influential campaigns to be automatically added to opportunities. When the automatic association is enabled, influential campaigns are added to opportunities when a campaign is related to a contact that is assigned a contact role on an opportunity prior to the close date of the opportunity. For example, if you have an email campaign with a member who is assigned a contact role on an open opportunity, the email campaign will be added to the Campaign Influence related list for that opportunity. 
Other options are incorrect because opportunities are usually influenced by more than one campaign, you have the option to automatically associate multiple influential campaigns to a single opportunity. If you don’t enable automatic association, users must manually add, edit, or delete influential campaigns in the Campaign Influence related list. 
Reference: 

https://help.salesforce.com/articleView?id=campaigns_influence_setup.htm&type=5