Final answer:
A virus is a microscopic infectious agent that consists of genetic material encased in a protein coat. The mass of a virus can range from a few femtograms to a few picograms, typically falling in the range of micrograms to milligrams. Grams and kilograms would be too large to estimate the mass of a virus.
Step-by-step explanation:
A virus is a microscopic infectious agent that can only reproduce inside host cells. It consists of genetic material, either DNA or RNA, encased in a protein coat called a capsid. The mass of a virus can vary depending on the type and size of the virus. On average, the mass of a virus ranges from a few femtograms (10^-15 grams) to a few picograms (10^-12 grams).
Therefore, when estimating the mass of a virus, it would typically be in the range of micrograms (10^-6 grams) to milligrams (10^-3 grams), depending on the size and type of the virus. Grams and kilograms would be too large of units to estimate the mass of a virus.