The chest-and-arm stretch squeezes
a. the pectoral muscles together
b. the biceps simultaneously
c. all muscles in the torso
d. the shoulder blades together

The correct answer is the shoulder blades together.

Streching is defined as a form of exercise in which a particular muscle or tendon is flexed or streched in such a way that it improves the elasticity of muscles to attain a better tone of muscle. Streching results in more flexibility of muscles. The scapula known as the shoulder blade connects the upper arm bone with the collar bone .The chest and arm strech aligns the shoulder blades and improve the posture and flexibility of the body.

for example, no new evidence will demonstrate that the earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the earth is not divided into solid plates that have moved over geological timescales .