<p>There are [rare] exceptions to the parallelism rule.
Consider
When<a href=“A”>/u</a> L’Enfant suggested to build<a href=“B”>/u</a> the United States Capitol at the center of<a href=“C”>/u</a> Washington, D. C., he also offered<a href=“D”>/u</a> to design a landscaped mall nearby. (E)</p>
<p>Nice parallel structure, right?
Well, the answer is “B”: the verb “suggest” should be followed by a gerund, not an infinitive.
When L’Enfant suggested building the United States Capitol at the center of Washington D.C., he also offered to design a landscaped mall nearby.
No parallelism no more. :)</p>