$1.90 \frac{1}{1-\sqrt[4]{3}}+\frac{1}{1+\sqrt[4]{3}}+\frac{2}{1+\sqrt{3}}$ The value is
(A) 1 .
(B) -1 .
(C) 2 .
(D) -2 .
(China Junior High School Mathematics League, 1990, 1999)
[Solution]
$$
\begin{aligned}
\text { Original expression } & =\frac{1+\sqrt[4]{3}}{1-\sqrt{3}}+\frac{1-\sqrt[4]{3}}{1-\sqrt{3}}+\frac{2}{1+\sqrt{3}} \\
& =\frac{2}{1-\sqrt{3}}+\frac{2}{1+\sqrt{3}} \\
& =\frac{4}{1-3}=-2 .
\end{aligned}
$$

Therefore, the correct choice is $(D)$
