Which of the following models refers to the gatekeeper concept?

The Westley and MacLean model refers to the gatekeeper concept, showing messages passing check points before reaching the audience.

It extends Newcomb's model and adds gatekeepers who select what the audience finally receives.

Newcomb's model is a balance model of two people and an object, without a gatekeeping stage.

Shannon and Weaver's model is a linear mathematical model centred on noise, not on gatekeepers.

George Gerbner's model stresses perception and the interplay of events and messages rather than a gatekeeper role.

In this model environmental factors, not the source, start the communication process.