The term Linking number [LK] defines a quantitative measure for
a) topologcal linkage of two complementary DNA strands in a double-stranded DNA molecule
b) action of topoisomerase enzymes
c) no. of subunits which constitute a functional lac repressor
d) no. of times the two complementary DNA strands wind about each other in a double-stranded DNA

answer can be multiple
my guess; d
im not sure whether d) alone is correct and IF a) is a correct option too