What is the double layered sac that surrounds the heart

If you relate the doppler effect on sound to the color of light waves, a police car would be the color as it approaches and the color as it recedes away from the observer.

Preventive health behaviors rarely have much influence on health as most diseases are genetic. a. true b. false

What do scientific models predict will happen to earth's temperature if current trends continue unmitigated? a. earth will heat and cool in a natural cycle b. earth will heat up and then return to an ice age c. earth will continue to warm at a rate of 0.25 c per decade d. earth will start to cool at a rate of 0.25 c per decade appex