Because the two strands of a dna molecule are to each other, either one can be used as a template to reconstruct the other

COMPLIMENTARY

Explanation:

Through a process known as DNA replication, a cell is said to divide into two and each new cell receives an exact copy of the DNA. They will both have one new and one parental strands respectively.  

Since these are identical copies, they also have an exact sequence of bases properly shared equally among the new cells and that makes it easier for us to use one strand as a template to create an exact sequence of bases in the other strand. This processes is called reconstruction.  

the 2nd option is the answer

the telephone is the answer