How is DNA copied in semi-conservative replication?

The original DNA molecule is the template for the new DNA molecules.

Two new DNA molecules form and the original DNA molecule dissolves.

The original DNA molecule is replaced by a complementary DNA molecule.

Two DNA molecules exchange complementary genes, forming two new molecules.

The first option would be how it would replicate semi conservative

The original DNA molecule is the template for the new DNA molecules.

Explanation:

First, the DNA strands uncoil and separate, forming a replication fork. Each strand acts as template for the formation of a new complementary DNA chain. One of the strands will be synthetized continuously, and it's called the leading strand, and the other one is formed discontinuously, in fragments called Okazaki fragments, and is referred to as the lagging strand. As product, there will be two new double stranded DNA molecules, each one of them containing a strand of the original molecule. That why the replication model is called semi conservative.