Which statement explains what geologists can learn from the graph?
they can estimate that all the potassium will have decayed within 6.5 billion years.
they can tell that 1/8 of the argon gas will be left after 3.9 billion years.
they can determine that a rock is 1.3 billion years old if 1/2 of the potassium has decayed.
they can see that potassium’s half-life varies from every 1.3 billion years to every 5.2 billion years.

They can determine that a rock is 1.3 billion years old if 1/2 of the potassium has decayed.

Explanation:

Geology refers to the solid, liquid, and gaseous matter that constitutes the solid  Earth and the processes by which they change over time.

It includes the study of other terrestrial planets as well.

A geologist is a scientist who studies geology.

He studies rocks and the Earth sciences.

A geologist can determine that rock is 1.3 billion years old if 1/2 of the potassium has decayed.

answer; the above statement is (true);

a.