Why shouldn't you use your thumb when taking a pulse apex?

An atom of nitrogen had seven protons in its nucleus. how many electrons does it have

Use the phylogenetic tree to the right to determine which statement below is true. organisms a and f are not related. organism e is more closely related to organism b than organism f. organisms c and d are more closely related than organisms a and b. phylogenetic trees

Ascientific idea becomes valid when it is what?