In Defining a Firm's Long-Run Average Cost Curve

In defining a firm's long-run average cost curve,

A) factor prices are held constant and technology is assumed to change.
B) factor prices are held constant and the quantity of factors of production used is varied.
C) factor prices are varied and the quantity of factors of production is held constant.
D) technology,factor prices,and the quantity of factors of production are all varied.
E) the time period must be longer than one year.