2. Let $M=\{$ isosceles triangles $\}, P=\{$ polygons with one side of length 1 and one interior angle of $36^{\circ} \},$ the number of elements in $M \cap P$ is ( ).
A. 2
B. 3
C. 4
D. More than 4
2. C.
$M \cap P$ can contain elements that are (1) isosceles triangles with a vertex angle of $36^{\circ}$ and legs of length 1; (2) isosceles triangles with a vertex angle of $36^{\circ}$ and a base of length 1; (3) isosceles triangles with a base angle of $36^{\circ}$ and legs of length 1; (4) isosceles triangles with a base angle of $36^{\circ}$ and a base of length 1.