Tenses:

Correct: Lucy traveled to Taiwan, met many Taiwanese people and made friends with them.

Incorrect: Lucy traveled to Taiwan, was meeting many Taiwanese people and made friends.

Correct: The doctor is seeing a patient now, and will see you in a short while.

Incorrect: The doctor is seeing a patient now, and sees you in a short while.

Infinitive form of verbs:

Correct: I like to sing, to travel and to meet new people.

Incorrect: I like to sing, traveling and meeting new people.

Gerund form of verbs:

Correct: Cooking is always fun for me, but singing not at all.

Incorrect: Cooking is always fun for me, but to sing not at all.

adjectives:

Correct: Children are happy, energetic and curious.

Incorrect: Children are happy, energy and curious.

nouns:

Correct: I eat a lot fruits and vegetables, and avoid sugar.

Incorrect: I eat a lot fruits and vegetables, avoid sweet. I eat a lot of fruits and vegetables and avoid sweet foods.

adverbs:

Correct: The student answered the questions correctly.

Incorrect: The student answered the questions correct.

Correct: The radio has announced the epidemic of swine flu lately.

Incorrect: The radio has announced the epidemic of Swine flu late.

prepositional phrases:

Correct: She is neither friendly nor polite.

Incorrect: She is neither friendly or polite.

Correct: You can come to dinner either tonight or Saturday.

Incorrect: You can come to dinner either tonight and Saturday.