Answer:
A
Explanation:
Upon discovery of the DNA structure by Watson and Crick, three models were proposed in the 1950's to explain the method in which DNA replicated. One of these models stood out, this model is the SEMICONSERVATIVE MODEL.
In the semiconservative model, it was proposed that a single DNA strand serves as a template for synthesizing its complementary strand. The cell replicates its DNA in the S-phase of interphase. In this phase, the the double-helix of the DNA is separated into two single strands. An enzyme called DNA polymerase then synthesizes a new strand complementary to each separated single strand.
At the end, the replicated double-stranded DNA now contains one old template strand and a new complementary strand.