I think the answer is b not too sure though
If a drug controls blood pressure than the transport of materials throughout our body will be affected. As for example - gases exchange, hormone level of every organ will be affected most. organs can develop hypoxia or hyperoxia conditions which can lead to cell damage or malfunction inside the organ and that can have a lethal effect on body also.
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.