18.47 Divide each corner of a rectangle into three equal parts, and connect the points of intersection formed by the two trisectors near the same side. The four points form
(A) a square.
(B) a rectangle.
(C) an irregular parallelogram.
(D) a rhombus.
(E) an arbitrary quadrilateral.
(4th American High School Mathematics Examination, 1953)
［Solution］From the given, we can prove
$$
\triangle A H E \cong \triangle B F E \cong \triangle C F G \cong \triangle D H G,
$$

which implies $\quad E F=F G=G H=E H$.
Also, since $A B \neq B C$, we can prove $E G \neq F H$. Therefore, the answer is (D).