The total number of stars in the observable universe is about

Select the correct answer from each drop-down menu. compared to its surroundings, the concentration of solutes is low inside a cell. so, the cell is with respect to its surroundings. a particular solute in this cell uses energy for its transport from the cell to its surroundings. this type of transport is called

The air that we breath is made mostly of which gaseous molecule

The heliocentric and the geocentric models of the solar system included these central principles