Reoviruses have been used to study viral pathogenesis in mice.Using virus reassortants, which of the following has been shown to be a major determinant for infection of the nervous system in a mouse?

A) Activation of the host cell immune system.
B) Binding of the virus to different host cell receptors.
C) Activation of the interferon system in host cells.
D) The rate of viral mRNA synthesis in host cells.
E) The rate of genome synthesis in host cells.