10. Let $I$ be the universal set, non-empty sets $P, Q$ satisfy $P \varsubsetneqq Q \varsubsetneqq I$. If a set operation expression containing $P, Q$ results in the empty set $\varnothing$, then this operation expression can be $\qquad$ (just write one expression).
10. $P \cap \complement_{1} Q$

Analysis The shaded part is $\complement_{1} Q$ (as shown in Figure (Question 10)).
Clearly, the required expression is $\complement_{1} Q \cap P=\varnothing$, or $\complement_{1} Q \cap(Q \cap P)$ or $\complement_{1} Q \cap(Q \cup P)=\varnothing$.
Comment This question tests the relationship and operations of sets.