Final answer:
The statement is false; viruses can range from 20 nm to over 1000 nm in size, and some large viruses exceed the 400 nm upper limit mentioned.
Step-by-step explanation:
It is false that most viruses range in size from 10 to 400 nm. While many viruses are indeed very small, typically around 20 to 250 nanometers in diameter, the size of viruses can vary greatly. Some of the more recent discoveries include viruses such as Pandoravirus salinus and Pithovirus sibericum, which can be up to 1000 nm in diameter. This shows that the size range of viruses exceeds the 400 nm upper limit mentioned in the question.
Most viruses cannot be seen with a light microscope and require an electron microscope for observation.Most viruses range in size from 20 to 250 nanometers. Some large viruses, such as the poxvirus, can be even larger. Although viruses are too small to be seen with a light microscope, they can be observed using electron microscopy. The recent discovery of giant viral species has further expanded our understanding of virus size.