Which of these has been used to hypothesize which continents were at one time joined

a. climates

b. magnetic crystals

c. glaciers

d. mountains

Magnetic crystals have been used to hypothesize which continents were at one time joined.

Option B

Explanation:

Magnetic crystals was another break through in the theory of plate tectonics which came two decades later (the theory talking about continental drift). Magnetic crystals are shaped like tiny bars of magnets.

These crystals point towards the direction of the magnetic north pole, when the lava cools down helping in finding the direction of the continent. This is popularly known as the magnetic polarity evidence.