I believe it's D don't take my word for it.
Doctors try to remove tumors from the body to prevent it from spreading and affecting other parts of the body.
Answer is for the earths core to cool enough for convection to stop, then the plates would have no convection current to move them.
Explanation: If the Earth's core were to cool down, the convection currents in the mantle would stop moving. Since the convection currents drive the plates, they would stop moving.
The poison dart frog suddenly increase if the predator that feeds off the dart frogs goes extinct or migrates to a different area then the dart fronts will have a much larger population.
This means that the resources the dart frogs rely on will start to diminish and their prey will have smaller numbers