How are the respiratory and circulatory systems similar?

A - Both systems provide glucose and other substances to cells.
B - Both systems regulate blood flow throughout the body.
C - Both systems help remove carbon dioxide from the body.
D - Both systems send messages to the nervous system for breathing.

It's B.

Explanation:

Both circulate blood flow throughout the body

the supermassive black hole is in the middle of the galaxy.

here is the answer

water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. weathering is the breaking down or dissolving of rocks and minerals on earths surface. once a rock has been broken down, a process called erosion transports the bits of rock and minerals away.