Which Is Not a Factor That Leads Geologists to Expect

Which is not a factor that leads geologists to expect that convection in the mantle is likely?

A) Viscosity in the lithosphere is high.
B) Viscosity beneath the lithosphere is lower because the rock is close to its melting temperature.
C) Some of the lithosphere is denser than the asthenosphere.
D) The thickness and mass of the mantle are huge.