1. Each interior angle of a convex polygon is $150^{\circ}$, then this convex polygon has ( ) diagonals.
(A) 42
(B) 54
(C) 66
(D) 78
-、1. B.
Since each exterior angle is $30^{\circ}$, the number of sides of this convex polygon is 12. Therefore, there are $\frac{12 \times 9}{2}=54$ diagonals.