which of the following could be true?

Question

If v1 is a vector containing some number of int elements sorted in ascending order, after these
statements execute:
std::vector results1;
std::vector results2;
std::unique_copy(v1.begin(), v1.end(), std::back_inserter(results1));
std::reverse_copy(v1.begin(), v1.end(), std::back_inserter(results2));
a. results1 contains more elements than results2.
b. The first element in results1 matches the last element in results2.
c. results1 is empty but results2 is not.
d. None of the above.

Answer 1

b. The first element in results1 matches the last element in results2.