2. In tetrahedron $P A B C$, $\angle A P B=\angle B P C=\angle C P A=90^{\circ}$, the dihedral angles formed by $\triangle P B C$, $\triangle P C A$, $\triangle P A B$ with $\triangle A B C$ are $\alpha, \beta, \gamma$, respectively. There are 3 propositions:
(1) $\cos \alpha \cdot \cos \beta+\cos \beta \cdot \cos \gamma+\cos \gamma \cdot \cos \alpha \geqslant \frac{3}{2}$
(2) $\tan ^{2} \alpha+\tan ^{2} \beta+\tan ^{2} \gamma \geqslant 0$
(3) $\sin \alpha \cdot \sin \beta \cdot \sin \gamma \leqslant \frac{1}{2}$
Which of the following are correct? ( )
A. (1)(2)
H. (2)
C. (1) (3)
1). (1)(2)(3)
2. $\mathrm{B}$

Take $\cos \alpha=\cos \beta=\cos \gamma=\frac{\sqrt{3}}{3}$ to know (1) and (3) are incorrect.
$\Sigma \tan ^{2} \alpha=\left(\Sigma \sec ^{2} \alpha\right)-3 \geqslant \frac{9}{\Sigma \cos ^{2} \alpha}-3=\frac{9}{1}-3=6$, so (2) is correct.