It is most important that a thesis statement
a. be clear and focused.
b. be short and simple.
c. have vivid descriptions and sensory details.
d. contain interesting content that grabs the reader's attention.

A. be clear and focused

A thesis is "a statement or theory that is put forward as a premise to be maintained or proved" (Google), and in order to maintain or prove a point, arguments must be clear and focused.

The answer is d