\textbf{This follows a geometric distribution.}  $$\mu = \frac{1}{p} = \frac{1}{0.10} = 10$$ 
\textbf{Ten percent of all trucks undergoing a certain inspection will fail the inspection. Assume that trucks are independently undergoing this inspection one at a time. The expected number of trucks inspected before a truck fails inspection is} 

(A) $$2$$ 
(B) $$4$$ 
(C) $$5$$ 
(D) $$10$$ 
(E) $$20$$ 