Which of the following is a primary source?

Newton's law of universal gravitation states that the force f between two masses, m1 and m2, is given below, where g is a constant and d is the distance between the masses. find an equation that gives an instantaneous rate of change of f with respect to d. (assume m1 and m2 represent moving points.)

Most energy in an ecosystem comes originally from_

The plum pudding model of the atom states that ?