Which of the following statements is true?
a. Nitrogen monoxide gases released by volcanoes can cause acid rain.
b. In 1812, Mauna Loa in Hawai'i erupted and caused the land mass of the island to increase by 7%.
c. The 1991 eruption of Mt. Pinatubo in the Philippines caused the entire planet to cool by 0.5 degrees Celsius.
d. Sulfur dioxide gases released by volcanoes cause pyroclastic flows.
