In the Search for Intelligent Life, Why Do Scientists Tend

In the search for intelligent life, why do scientists tend to assume that its biochemistry is more likely to be based on the element carbon than on any other element?

A) Carbon is the most versatile element, combining with the largest number of other elements in many different ways to produce long-chain molecules.
B) Carbon is the only element that can combine into ring-shaped molecules, which is the shape of life-form molecular structure.
C) Carbon releases far more energy than do other similar atoms when it combines with other elements, a process that is essential for the support of life.
D) Scientists expect that life will mimic that on the surface of Earth, which is carbon-based.