Question

28
seafloor spreading and continental drift are both caused by
a tides
b convection currents in the mantle
c changes in earths magnetic field
d shrinkage of the crust as the earth cools

Explanation:

Seafloor spreading and continental drift are driven by the slow, circular movement of rock in Earth's mantle. These convection currents transfer heat from the core, pushing tectonic plates apart (seafloor spreading) and moving continents. Tides, magnetic field changes, and crustal shrinkage do not cause these large-scale tectonic movements.

Answer:

B. convection currents in the mantle