Viruses use the host's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally have. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires

Explanation:

Virus do not replicate without host. They use the host's machinery to replicate their genome and make copies of themselves. The genome of virus contains genes for their own enzymes, like reverse transcriptase and protease. So virus infect human cell by injecting their genome into human cell and replicate their genetic material by using host's machinery to make all required enzymes. The virus has  its own genome and contain genes that code for any specialized enzymes that virus need  that the host does not  have.

Answer;

Basaltic igneous rock

Explanation;

-Basaltic igneous rock is dense and has a dark color.

Igneous is among the three types of rocks, others being sedimentary and metarmophic rocks. It is formed as a result of cooling and solidification of magma or lava.

-Basalt is an extrusive igneous rock that is dark in color, and occurs in the ocean bedrock and may also occur on land in extensive flows of lava. Additionally, basalt contains fine grains and is composed of mainly pyroxene and plagioclase minerals.