11. Claire measures the degree of the interior angles of a convex polygon and calculates their total sum to be $2017^{\circ}$. At this point, she realizes she forgot to include one angle in her calculation. Then, the angle she forgot is ( ).
(A) $37^{\circ}$
(B) $63^{\circ}$
(C) $117^{\circ}$
(D) $143^{\circ}$
(E) $163^{\circ}$
11. D.

Notice that the sum of the interior angles of a convex polygon is a multiple of 180.

Given $\left\lceil\frac{2017}{180}\right\rceil=12$ (where $\lceil a\rceil$ denotes the smallest integer not less than the real number $a$), and $12 \times 180=2160$, we know that the angle Claire forgot is congruent to $2160-2017=$ 143 modulo 180.

Since it is an interior angle of a convex polygon, this angle is $143^{\circ}$.