Which of the following are ways in which a geologist may determine the density of earth materials?

A) through direct measurement in the laboratory
B) by measuring the different velocities of seismic waves
C) using instruments to measure the pull of gravity
D) all of these

All the methods listed are used by geologists to determine the density of Earth materials. Direct measurement in the laboratory provides precise density values for samples. The velocity of seismic waves, which changes depending on the density and composition of the materials they travel through, offers insights into the density of materials beneath the Earth's surface. Instruments measuring gravitational pull can infer density variations because denser materials exert a stronger gravitational force.