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Answer:
A
Step-by-step explanation:
DNA replication follows semi conservative model. The two original strands separate from each other and each strand acts as a template for replication. Newly synthesized DNA molecule has one original strand and one newly synthesized strand.
Here, the original strands are depicted by thick lines and newly synthesized strands are depicted by thin lines. DNA molecules in option A have one old and one new strand in each DNA molecule (one thick and one thin line). Hence, option A is correct.