An advertiser working in Display & Video 360 created a line item for their mobile web campaign and accidentally targeted mobile in-app. The mobile in-app targeting was quickly removed at the insertion order level, but the campaign continues to target mobile in-app. What is the issue here?

You can’t modify targeting once the campaign has line items assigned.
You can’t modify insertion order targeting at the line item level.
You can’t modify targeting for mobile in-app inventory.
You can’t modify existing line item targeting at the insertion order level.