This sounds like an intestinal blockage and is a life threatening condition. I would get the dog to the nearest emergency clinic ASAP!!!
looking up homework questions are we know?
Waste is removed through a designated opening
The mouth is the opening through which food enters the body. From the mouth, food moves to the esophagus, stomach, intestines, and rectum before the undigested solid food waste exits at the anus.
A) Only one opening: they expel undigested material through the mouth.
Why are you looking for an opening?
In most lower animals there is two-way digestion, where the food enters the stomach or a cavity, and then the undigested remains exit the animal through the same opening.
The word you're looking for is "entrance."
I believe you would be looking for the country opening up for immigration.
A Cat fish
White, sweet smelling smoke coming out of tail pipe and or air bubbles constantly bubbling out of radiator cap opening with cap off.
Looking at Forever by Tim Truman
a vent