List and describe three of the body's physical or chemical barriers against infection

Barriers against the infection:
1.               Skin- It is the first line of defence (physical) which prevents invasion by microorganisms. Skin protects the body unless it is damaged, by an injury or burn.
2.               Mucous membranes- It is a barrier that envelops the mouth, nose, and eyelids. Tears, mucus and saliva are a part of this defence and they contain enzymes that break down the cell wall of many bacteria.
3.               The digestive tract-Beside its main function, it can be an effective barrier, because of stomach acid, pancreatic enzymes, bile, and intestinal secretions. These components can kill bacteria or prevent their multiplying.

Answer:

the statements that apply here about binary star system are

"have stars that might appear to wobble"

"often have one star that is brighter than other"

a binary star is a star system consisting of two stars revolving around their common barycenter. systems of two or more stars are called multiple star systems.