Answer:
Platysma.
Step-by-step explanation:
Platysma is the sheet of muscle that arise from the chest and deltoid muscle. The muscle rises over the clavicle.
Platysma muscle comes upward from the slanting manner by the sides of the neck. This muscle draws the corners of the mouth and lower lip. Hence, platysma muscle is used to express horror and for the pouting.
Thus, the answer is platysma.