Why Does Magma Viscosity Vary with Silica Content

Why does magma viscosity vary with silica content?

A) Increasing silica increases a tendency for silica bonds to link up in networks,acting like a polymerization of the magma.
B) Increasing silica content lowers the melting temperature and since increasing the temperature of a magma decreases viscosity increasing silica content increases viscosity.
C) Increasing silica content increases the amount of water a magma can dissolve and water decreases magma viscosity,so increasing silica content decreases magma viscosity.
D) There is no correlation between silica content and magma viscosity.