Check all statements that are equivalent to if the sky is not clear, then you don't see the stars ? a. clear sky is necessary and sufficient for seeing the stars. ? b. if the sky is clear, then you see the stars. c. you don't see the stars unless the sky is clear. ? d. clear sky is necessary to see the stars. e. the sky is clear only if you see the stars. f. clear sky is sufficient to see the stars. g. if you don't see the stars, then the sky is not clear. h. if you see the stars, then the sky is clear. i. you see the stars only if the sky is clear.