Which is a binary star? a) algol b) the sun c) alpha centauri d) polaris e) the big dipper

Alpha Centauri d is the sure fire answer

Alpha Centauri

Explanation:

A binary star is a system of two stars, one revolving around the other or both revolving around a common center. It should not be confused with the two stars that appears close in the sky with the naked eye. Binary stars are classified as eclipsing binaries, visual binaries, astrometric binaries and spectroscopic binaries.

Stimulus is something that causes a reaction, especially interest, excitement or energy. An example of stimulus is a shiny object for a baby. Receptors in muscles provide the brain with information about body position and movement. The brain controls the contraction of skeletal muscle. The nervous system regulates the speed at which food moves through the digestive tract.