In 1991, the massive eruption of mt. pinatubo caused global temperatures to

a) increase because sulfur in the stratosphere absorbed solar radiation
b) drop because sulfur in the stratosphere reflects solar radiation
c) drop because the carbon dioxide added to the atmosphere destroyed the ozone layer
d) increase because lava is extremely hot and adds this heat to the air

Option B is correct.

Explanation:

The explosion of Mount Pinatubo has been one of the biggest volcanic eruptions in history. The explosion released about 15 - 30 million tons of sulfur dioxide to the atmosphere; this sulfur, when combined with water and oxygen, becomes sulfuric acid. The size of the sulfur dioxide cloud was such that eventually the entire planet was covered with a layer of this gas, and when the sulfuric acid was formed, it reflected a portion of the sun's radiation.

By August 1993, the entire planet suffered a temperature reduction of about 0.73 C.