Why is DNA replication called simi conservative

As the DNA double helix is unwound by helicase, replication occurs separately on each template strand in antiparallel directions. This process is known as semi-conservative replication because two copies of the original DNA molecule are produced. Each copy contains one original strand and one newly-synthesized strand.

Explanation:

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

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c.           is the correct answer