One of your line items has high performance but low delivery.How should you adjust your supply to optimize a campaign for better performance and delivery?

The correct answer is "Add additional supply." If a line item shows high performance but low delivery, it means the campaign is effective when it runs, but it isn't running enough to meet its potential. By adding additional supply, you provide more opportunities for your high-performing ads to be shown, which will increase delivery without sacrificing performance. Reducing supply would further limit delivery and prevent the campaign from reaching its full potential.