6. As shown in Figure 1, fold up the five "corners" (isosceles small triangles) of the regular pentagram along their bases, so that they form right dihedral angles with their original planes. In the resulting spatial figure, there are ( ) pairs of skew line segments.
(A) 45
(B) 50
(C) 55
(D) 60
6. B.

The outer boundary of the pentagram is a closed zigzag line composed of 10 line segments, which are alternately colored red and blue (the inner small pentagon is not colored), as shown in Figure 4. Among these 10 line segments, any pair of the same color are skew, while any pair of different colors are coplanar, thus yielding $2 C_{5}^{2}=20$ pairs of skew line segments; also, each colored line segment is skew with exactly three sides of the inner small pentagon, resulting in 30 such pairs. Therefore, there are a total of 50 pairs of skew line segments.