Question: Identify the congruent triangles in the figure.
Left top: triangle $PQR$, right angle at $Q$; $P$ is top-left, $Q$ is top-right, $R$ is bottom.
Right top: triangle $NMO$, right angle at $N$; $N$ is top-left, $M$ is top-right, $O$ is bottom.
A $\triangle OMN \cong \triangle RPQ$
B $\triangle MNO \cong \triangle RQP$
C $\triangle NOM \cong \triangle RQP$
D $\triangle NMO \cong \triangle RPQ$
1. **Problem Statement:** Identify which pair of triangles are congruent among the options given.
2. **Triangles Description:**
- $\triangle PQR$ with right angle at $Q$.
- $\triangle NMO$ with right angle at $N$.
3. **Congruence Criteria:** For two right triangles to be congruent, we can use the RHS (Right angle-Hypotenuse-Side) criterion.
4. **Check each option:**
- Option A: $\triangle OMN \cong \triangle RPQ$
- Note the order of vertices matters. $OMN$ means right angle at $M$ (since $N$ is second), but $\triangle NMO$ has right angle at $N$, so this order is inconsistent.
- Option B: $\triangle MNO \cong \triangle RQP$
- $MNO$ means right angle at $N$ (middle vertex), matching $\triangle NMO$'s right angle at $N$.
- $RQP$ means right angle at $Q$ (middle vertex), matching $\triangle PQR$'s right angle at $Q$.
- So both triangles have right angles at the middle vertex.
- Option C: $\triangle NOM \cong \triangle RQP$
- $NOM$ means right angle at $O$ (middle vertex), but $\triangle NMO$ has right angle at $N$, so order is inconsistent.
- Option D: $\triangle NMO \cong \triangle RPQ$
- $NMO$ means right angle at $N$, matching $\triangle NMO$.
- $RPQ$ means right angle at $P$, but $\triangle PQR$ has right angle at $Q$, so order is inconsistent.
5. **Conclusion:** Only option B correctly matches the right angles and vertex order.
**Final answer:** $\boxed{\triangle MNO \cong \triangle RQP}$