In the planetary model, electrons . do not exist
are shown in a cloud
have positive charges
orbit the nucleus like the planets orbit the sun

Secondary pollutants are more harmful than primary pollutants. select the best answer from the choices provided ot of

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?

Which kind of worm has a closed circulatory system? a planarian b fluke c pinworm d an earthworm