Answer:
1. When things go wrong, Carl tends to brood for hours and to blame others.
3. The school was closed not only because of the snow and ice but also because of the lack of heat
4. The ice was a greater problem for the electrical power company than for the natural gas company.
Explanation:
Parallel structure refers to sentences constructions that have two or more words, phrases or clauses that are grammatically similar or identical in their structure. It is often used to show that the ideas with the same grammatical form (or structure) are equally important, to give a natural flow to the reading and to make it easier to process.
Sentence 1:<em> When things go wrong, Carl tends to brood for hours and to blame others</em> uses parallel structure because it uses the infinitive verb twice: <em>to brood </em>and<em> to blame.</em>
Sentence 3: <em>The school was closed not only because of the snow and ice but also because of the lack of heat </em>is also correct because it has two phrases with the same grammatical form:<em> </em><em>because of the snow and ice</em><em> </em>and<em> because of the lack of heat.</em>
Lastly, in the sentence 4:<em> </em><em>The ice was a greater problem for the electrical power company than for the natural gas company</em>, the phrases<em> the electrical power company </em>and<em> the natural gas company</em> use parallel structure too.