Just as Terri was driving in sight of a billboard for Chipotle Mexican Grill, a small child darted out into the street in front of her. Terri was so concerned with avoiding the child that she totally missed the restaurant's billboard. In terms of the communication process, Chipotle acted as:

Answer: Main message or source

Explanation: According to the situation that is described in the question, Chipolte is acting as the main source or message for Terri as she was aiming to get the Mexican grill from there. Reaching Chipolte was missed by her due to the small child on the street.

The small child was acting as the noise source which distracted her from reaching Chipolte. She tried to protect the child while driving and because of that her destination (Chipolte) was missed.