An Independent variable is a variable that changes or is controlled during an experiment, so according to this information your correct answer will be A) the coconut juice.
Finches adapt to the new conditions such as drought by changing the size, shape and depth of their beaks. Beak morphology varies according to drought conditions. Since after the drought, vegetation dries out and the hard, big, tough seeds remain, only the finches with deep beaks will survive. Finches adapt via their beaks to different foods sources and different local conditions.
If the original strand is TACGGTACCGGA, the complementary strains is ATGCCATGGCCT