Complex sentence: Manganese dioxide decomposes above about 530 ° C to manganese (III) oxide and oxygen, whereas hot concentrated sulfuric or hydrochloric acid reduce the Mn IV to manganese (II).
Split into simpler sentences: Manganese dioxide decomposes above about 530 ° C to manganese (III) oxide and oxygen. Hot concentrated sulfuric reduces the Mn IV to manganese (II).