$33 \cdot 48$ If the integer part of $5-\sqrt{3}$ is $x$, and the decimal part is $y$, then the value of $2 x^{3}-$ $\left(y^{3}+\frac{1}{y^{3}}\right)$ is 
(A) 2.
(B) -2.
(C) $\sqrt{3}+2$.
(D) $2+3 \sqrt{3}$.
(E) $2-6 \sqrt{3}$.
(Chongqing, Sichuan Province, China Junior High School Mathematics Competition, 1983)
[Solution] From the given, we know $x=3, y=2-\sqrt{3}$, thus
$$
2 x^{3}-\left(y^{3}+\frac{1}{y^{3}}\right)=2 \cdot 3^{3}-\left[(2-\sqrt{3})^{3}+\frac{1}{(2-\sqrt{3})^{3}}\right]=2 \text {. }
$$

Therefore, the answer is $(A)$.