We laugh at jokes, but seldom about how they work.
A. we think
B. think we
C. we do think
D. do we think
网友回答
A. we think
B. think we
C. we do think
(答案→)D. do we think
解析：原句意思，我们因笑话而发笑，却很少思考它们的作用。含有否定意义的副词如no, never, little, seldom, hardly 等位于句首时，要将助动词、情态动词或系动词放在主语前面，构成部分倒装。seldom 为否定副词放句首，用部分倒装。