Question

what 2 sulfur - containing gases are released by volcanoes?
carbon monoxide
sulfur dioxide
hydrogen sulfide
carbon dioxide

Explanation:

Volcanoes release sulfur-containing gases. Sulfur dioxide ($SO_2$) is a primary sulfur gas from volcanic eruptions. Hydrogen sulfide ($H_2S$) is another sulfur-containing gas emitted by volcanoes. Carbon monoxide and carbon dioxide do not contain sulfur.

Answer:

sulfur dioxide, hydrogen sulfide