A palindromic sequence is a nucleic acid sequence on double-stranded DNA or RNA wherein reading 5' (five-prime) to 3' (three prime) forward on one strand matches the sequence reading 5' to 3' on the complementary strand with which it forms a double helix. This definition of palindrome thus depends on complementary strands being palindromic of each other. So the correct option is 'Palindromic sequence of base pairs'.