Which type of viral RNA has the same base sequence as mRNA and functions as a template for protein synthesis during viral replication?

The correct choice highlights the characteristics of positive-sense RNA. This type of viral RNA is directly comparable to messenger RNA (mRNA) because it contains the same base sequence and can be immediately translated by the host's ribosomes into proteins. This means that once a virus with positive-sense RNA enters a host cell, the RNA can be directly read to synthesize viral proteins, facilitating the viral replication process.

Positive-sense RNA viruses utilize their genomic RNA as mRNA, allowing for rapid production of viral components upon infection. This feature is fundamental to their lifecycle, as it enables efficient manipulation of the host's cellular machinery for the virus’s benefit.

In contrast, other types of viral RNA, such as negative-sense RNA, would need to be converted into a positive-sense form before they can be translated into proteins. Retroviral RNA also goes through a reverse transcription process to generate DNA before becoming part of the host's transcription processes. Similarly, translatable RNA is not a standard term used in the context of viral RNA classifications. Thus, positive-sense RNA is unique in its immediate usability for protein synthesis in the context of viral replication.