The correct option is B Both A and R are true and R is the correct explanation of A
Geologists believe the molten rock deep within the earth circulates by convection currents. Due to temperature and pressure differences, the hot fluids tend to rise, whereas cold fluids tend to sink. This creates a current within the fluid called Convection current. According to geologists, convection currents within the earth are a contributing cause of volcanoes, earthquakes, and continental drift. Apart from radiation and conduction, convection is also a process of transfering heat energy. The process of convection can also be observed in the movement of ocean currents and the circulation of air in the Earth's atmosphere.