3) Errors in Parallelism

Parallelism basically demands adherence to a proper structure in a sentence. Words need to be in a correct form.
eg.1) Reena loves to sing, cricket and dancing (Wrong)
Reena loves to sing, play cricket and dance (Either use the to......to form or the ing.......ing form)(Correct form of the activity, consistency in the use of participles and gerunds)

eg.2) The children loved the merry-go-round, the roller-coaster, the giant wheel and the swinging (Wrong)
The children loved the merry-go-round, the roller-coaster, the giant wheel and the swing. (Use noun form throughout)

eg.3) All business students should learn word processing, accounting, and how to program computers (Wrong)
All business students should learn word processing, accounting, and computer programming (Parallelism of verbs)

eg.4) The French, the Italian, Portuguese and British are attending the concert. (incorrect)
The French, the Italian, the Portuguese and the British are attending the concert.
(Correct use of article or preposition throughout)

eg.5) The students hit upon an innovative, inspiring, motivating thought that was beneficiary. (incorrect)
The students hit upon an innovative, inspiring, motivating and beneficial thought.
(Parallelism in adjectives)

eg.6) I wish to either join IIMA or XLRI (Incorrect)
I wish to join either IIMA or XLRI.(Common verb 'join',it will come before either...or)

eg.7) I wish to take either my parents to the cinema or go by myself.
I wish to either take my parents to the cinema or go by myself.(Uncommon verbs 'take' and 'go')

eg.8)Those who read and travel are likely to be more knowledgeable than the people who read but don't travel.(Incorrect)
Those who read and travel are likely to be more knowledgeable than those who read but don't travel.(Parallelism in pronouns)

eg.9)Smriti is tall, fair, beautiful and angry. (Incorrect)
Smriti is tall, fair and beautiful.(Do not compare abstract with concrete)

eg.10)I have been to Paris and saw the Niagara falls. (Incorrect)
I have been to Paris and have seen the Niagara falls. (Consistency in Tenses)

eg.11)Peter is famous more for his ability than how big his muscles are.(Incorrect)
Peter is famous more for his ability than his strength.(Consistency in comparisons)

eg.12)Ramesh like watching movies more than his sister.(Incomplete comparisons)
Ramesh likes watching movies more than his sister does.

eg.13) He has both experienced the joys of innovation and the sorrows of redundant efforts (incorrect)
He has experienced both the joys of innovation and the sorrows of redundant efforts.
(Place correlative conjunctions immediately before the parallel terms)

eg.14) One must read good books if you wish to do well in English.(Pronoun shifts)
One must read good books if one wishes to do well in English.