An Isilon Has Two Ports Configured Per Node

An Isilon has two ports configured per node. Each port is on a different VLAN. Although incoming traffic is evenly distributed, transmitted data from the Isilon uses one port more than the other port. What could be the cause of this imbalance?

A) Static routes are configured on the less-used port
B) A default gateway was not configured on both ports
C) Source Based Routing is not enabled on the cluster
D) Priority of the gateway in the less-used port set too low