2. For a regular tetrahedron $ABCD$ with edge length 1, points $P, Q$ lie on segments $AB, CD$ respectively. The range of the distance between points $P, Q$ is
A. $[1,+\infty)$
B. $\left[\frac{\sqrt{3}}{2}, 1\right]$
C. $\left[\frac{\sqrt{2}}{2}, 1\right]$
D. $\left[\frac{1}{2}, 1\right]$
2. $\mathrm{C}$ It is easy to know that the maximum distance between points $P$ and $Q$ is $A C=1$;

When $P$ and $Q$ are the midpoints of segments $A B$ and $C D$ respectively, the distance between them is the distance between the skew lines $A B$ and $C D$, which is $\frac{\sqrt{2}}{2}$. This is the shortest distance between any two points on the skew lines $A B$ and $C D$.
In summary, the range of distances between points $P$ and $Q$ is $\left[\frac{\sqrt{2}}{2}, 1\right]$.