1. As shown in Figure 1, 16 different right-angled triangular paper pieces are used to form a snail shape. The positions of the right angles and the line segments of length 1 are already marked. The integer value closest to the perimeter of this snail shape is ( ).
(A) 19
(B) 20
(C) 21
(D) 22
- 1. C.

From Figure 1, we know $O A=\sqrt{17}$.
Therefore, the perimeter of the seashell shape is $17+\sqrt{17}$, the closest integer is 21.