Thefollowing sentences are from one paragraph. Decide which one is the topic sentence of the paragraph?1)In time, this melted part rises as a magma.2)The formation of a volcanic eruption is a dramatic series of events.3)As the plate sinks, friction and the earth’s heat cause part of it to melt.4)The magma produces heat, steam, and pressure.5)First of all, most volcanoes are formed where two plates collide.6)Then one of the plates is forced under the other and sinks.7)When the heat, steam, and pressure from the magma finally reach the of the Earth, volcanic eruption occurs.