"RNA retroviruses use" A. use restriction enzymes to replicate and transcribe their genomes. B. viral reverse transcriptase to make a DNA copy that is integrated into the host genome and then host RNA polymerase transcribes it. C. host DNA polymerase to replicate their genome and host RNA polymerase to transcribe it. D. viral RNA-dependent RNA polymerase to replicate their genomes and transcribe it.

B. viral reverse transcriptase to make a DNA copy that is integrated into the host genome and then host RNA polymerase transcribes it.

Explanation:

RNA retrovirus when enters into its host cell it first use its reverse transcriptase enzyme and converts its RNA genome into the DNA so that viral DNA can be incorporated into the host cell and it can be replicated with the host cell.

One of the famous example of RNA retrovirus is HIV which infect CD4 cells and converts its RNA into cDNA with the help of reverse transcriptase enzyme and then this DNA enters the nucleus of the cell and incorporates into the host genome. Then it use host machinery to be transcribed. So the correct answer is B.

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many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.