Answer:
B. A DNA molecule has two paired strands.
Step-by-step explanation:
DNA is a double helical structure in which two DNA strands are joined together by complementary base pairing between the bases of two strands.
The tendency of a single-stranded DNA to base pair with another single-stranded DNA or RNA with a complementary sequence allows a probe to locate a gene in a single-stranded DNA.
Probes are the short polynucleotide strands with a complementary sequence to that of the gene under study. Therefore, probes bind to the genes with complementary sequences and help locate them in a long single-stranded DNA.