5. A triangular pyramid has three lateral faces, two of which are isosceles right triangles, and the other is an equilateral triangle with a side length of 1. Then, the volume of this triangular pyramid ( ).
(A) has a unique value
(B) has 2 different values
(C) has 3 different values
(D) has more than 3 different values
5. (C).
(1) As shown in Figure 2 (1), if $S A=S B=S C=B C=1$, $S A \perp S B, S A \perp S C$, then $V_{S A B C}=V_{A S B C}=\frac{\sqrt{3}}{12}$;
(2) As shown in Figure 2 (2), if $S B=S C=B C=1, S A=\frac{\sqrt{2}}{2}$, $S A \perp A B, S A \perp A C$, then $V_{S A B C}=\frac{\sqrt{2}}{24}$;
(3) As shown in Figure 2 (3), if $S A=S B=A B=A C=B C=1$, $S C=\sqrt{2}, S A \perp A C, S B \perp B C$, then $V_{S A B C}=V_{A S B C}=\frac{\sqrt{2}}{12}$.