4. Which of the following figures cannot be drawn in one stroke without retracing any line? ( )
将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。
Problem 352
Official solution
\begin{tabular}{l}
4 \\
\hline
\end{tabular}
4. Which of the following figures cannot be drawn in one stroke without retracing any line? ( )
将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。
\begin{tabular}{l}
4 \\
\hline
\end{tabular}