1. The sum of the interior angles of a convex $n$-sided polygon is less than $1999^{\circ}$. Then, the maximum value of $n$ is ( ).
(A) 11
(B) 12
(C) 13
(D) 14
$-1 .(\mathrm{C})$.
Since the sum of the interior angles of a convex $n$-sided polygon is $(n-2) \cdot 180^{\circ}$, we have $(n-2) \cdot 180^{\circ}<1999^{\circ}, n-2<12, n<14$.
Moreover, the sum of the interior angles of a convex 13-sided polygon is
$$
(13-2) \times 180^{\circ}=1980^{\circ}<1999^{\circ} \text {, }
$$

Therefore, the maximum value of $n$ is 13.