Parallel construction means that you
a. use the same grammatical construction in all similar headings throughout an outline.
b. begin each paragraph of your essay in the same way.
c. give both sides of the argument in your essay.
d. repeat the first paragraph of your essay as the last paragraph.

a. use the same grammatical construction in all similar headings throughout an outline

Using the same grammatical construction in all similar headings throughout an outline is called parallel construction. Parallel construction is also known as parallelism. This means that two or more ideas has the same degree of importance in the sentence therefore it should be written or stated grammatically equal. This can also help in establishing the clarity of the idea you want to convey in the sentence. Some examples of parallelism are the following :

of loving so much
of hating too hard
of crying so long

This one might be 1 hope