How have astronomers formed their ideas about the layers of the sun? O developing mathematical models based only on known data
O making direct observations of the sun's layers
O observing all the layers during total solar eclipses
O using theoretical models combined with known data

Why should the united state be concerned about air pollution in china?

How does the study of genetic disorders such as pku biologists understand normal alleles?

Multicellular organisms use cell division, mitosis, for growth and the maintenance and repair of cells and tissues. single-celled organisms may use cell division as their method of reproduction. regardless of the reason for mitosis, the process ensures genetic continuity. what is the step in the cell cycle that ensure genetic continuity?