# Stereochemistry of meso compounds

I got tripped up by this question; I thought these were all enantiomers when in fact they were all meso compounds.

How can one prevent this from happening?

How does one rotate the Fischer projection, for example, in the first problem; I understand that one has to hold one group in place, but then what?

To rotate on a single bond in a Fischer Projection, all 3 groups move in the same direction. $\frac {1} {2\ \ \ 3} \rightarrow \frac {2} {3\ \ \ 1}$. See this page for more information.
a) $\ce{CH3<->H}$ THEN $\ce{H<->OH}$
b)Rotate nearer $C$ by $\pi/3$ rad. anticlock wise.
c)Imagine rotation about $C_2-C_3$ by $\pi$ rad., the $OH$ in the right back of the plane comes in front projecting out towards us hanging down and thus we have a vertical plane of symmetry.