Parallel Construction: // 
¡@
   
EXPLANATION: 

Similar ideas in a sentence had better be grammatically alike. That is, they have to be written in the same form. Otherwise, the sentence will appear very awkward.  
 

Nonparallel (Awkward Sentence) Parallel (Revised Sentence) 
Seeing is to believe. Seeing is believing. 
I saw him falling in love, to become lovelorn, and he married a woman he hardly knew. I saw him falling in love, becominglovelorn, and finally marrying a woman he hardly knew.
I bought food for the hamster, dog, and the cat. I bought food for the hamster, the dog and the cat.  
OR

I bought food for the hamster, dog, and cat.
My teacher graded my composition as underdeveloped, poorly organized, and not having coherence. My teacher graded my composition as underdeveloped, poorly organized, and incoherent.
Your excuse is not only unreasonable but (also) I find it hard to believe. Your excuse is not only unreasonable but unbelievable.
I believe that love is definitely more important than having money. I believe that love is definitely more important than money.
My friend was nicely served; I did not have good service.  
OR

My friend was nicely served, while the waiter gave me poor service.

 		My friend was nicely served; I was not.  
OR

My friendly was nicely served, while I was not.
Students can be generally divided into three types: those who never study; those who only cram before exams; and diligent students. Students can be generally divided into three types: those who never study; those who only cram before exams; andthose who study day andnight.
My experience as a freshman is both exciting and I will never forget. My experience as a freshman is both exciting and unforgettable.
Such as  ¡@
NB:   
1.  When using phrases such as ¡§not only ¡K but also,¡¨ ¡§whether ¡K or,¡¨ ¡§more ¡K than,¡¨ ¡§either ¡K or,¡¨ ¡§both ¡K and,¡¨ ¡§such as,¡¨ you have to check if parallel construction is needed.
2.  When a sentence contains a series of items, these items must be in the same form.   (Commasor coordinating conjunctions may connect the series of items.)
3.  When you compose a thesis statement of an essay or a topic sentence of a paragraph that lists several points, be sure to put them in parallel form.
 
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