1. Given that $\cos 78^{\circ}$ is approximately $\frac{1}{5}, \sin 66^{\circ}$ is approximately ( ).
A. 0.92
B. 0.85
C. 0.88
D. 0.95
1. B. $\sin 66^{\circ}=\cos 24^{\circ}=1-2 \sin ^{2} 12^{\circ}=1-2 \cos ^{2} 78^{\circ}=1-2 \cdot \frac{2}{25}=1-0.16 \approx 0.84$.