We Proved, Using Einstein's Two Basic Principles, That If Velma

We proved, using Einstein's two basic principles, that if Velma is moving past Mort then Mort should observe Velma's clock to go slow. This behavior of Velma's clock occurs because, as observed by Mort,

A) the light beam in Velma's light- clock travels at slower than the normal lightspeed.
B) the light beam in her light- clock travels less than 300,000 km during one of Velma's ticks.
C) the light beam in Velma's light- clock travels at faster than the normal lightspeed.
D) the light beam in her light- clock travels further than 300,000 km during one of Velma's ticks.
E) Velma's light- clock shortens along its direction of motion.