Please help I dont understand, Thanks Brainliest to the first correct person to answer.

Ozone in the upper atmosphere has been depleted by a. sulfur dioxide. b. chlorofluorocarbons. c. carbon dioxide. d. oxygen.

Which statement about portugal is not true? a. it granted independence to its last colony in 1975 b. it has avoided conflict with spain c. it was a leader in european world exploration in the 1400s d. its economy is changing from agricultural to industrial b. it has avoided conflict with spain

Sink holes may eventually for to join a. wide valleys b. zone of aeration c. dripstones d. aquifer