An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach. Some antacids have been used in the treatment of constipation and diarrhea. Marketed antacids contain salts of aluminum, calcium, magnesium, or sodium.
Perceptual set is the tendency to perceive certain things and ignore others, in this case Jill is known as a 'selector' because she has certain expectations and focuses her attention on the loud children instead of the quiet ones.
