What is the importance of dust, volcanic ash, & salt in the atmosphere

Ithink the answer to that would be b):

Answer(12) judaism; ans(11) all of the above; //ans(10) islands that are artificially created; //ans(9) people accept that the caste system keeps order in society and prevent chaos; ///ans(8),brahman; ans(7) the sikhns; ///ans(6); the non-cooperation movement; asn(5)sporadically grant congressional requests; /ans(4) all of the above; ///ans(3) true; //ans(2) true; //ans(1) false;