A fast-food chain, Bob's Bigger Burgers, has just launched a campaign to market its new pound-and-a-half burger against its competitor, Lou's Burgers, who previously sold the biggest burger at a pound and a quarter. Bob's Bigger Burgers' strategic move against Lou's Burgers is a:

Competitive action.

Explanation:

A competitive action is an action taken by a business to gain a competitive advantage over other business offering similar product to theirs. Bob's Bigger Burgers has taken a competitive action by increasing the size of their burgers to be larger than that of Lou's Burgers their competitors.