Some lawyers working for the Department of Justice worry that Google is abusing its power and behaving like a monopoly in the way it charges for ads. What type of suit would it be if the Department of Justice filed a lawsuit?

The lawsuit would be antitrust.

Explanation:

The antitrust laws can be defined as the federal and states laws which are expected to keep the business workings or operations impartial and fair. These laws regulate the working style of companies. In simple words, the laws ensure the business companies to not to gain too much power in the free playing market.

The antitrust laws keep an eye the working on the business companies to form monopoly by taking certain actions. These laws put ban on the misleading business practices by which the companies use their power to create monopoly in the market.