$28 \cdot 35$ continued fraction $-\frac{1}{2-\frac{1}{2-\frac{1}{2--\frac{1}{2}}}}$ is 
(A) $\frac{3}{4}$.
(B) $\frac{4}{5}$.
(C) $\frac{5}{6}$.
(D) $\frac{6}{7}$.
(E) $\frac{6}{5}$.
(26th American High School Mathematics Examination, 1975)
[Solution] $\frac{1}{2-\frac{1}{2-\frac{1}{2-\frac{1}{2}}}}=\frac{1}{2-\frac{1}{2-\frac{2}{3}}}=\frac{1}{2-\frac{3}{4}}=\frac{4}{5}$.
Therefore, the answer is $(B)$.