Your listener can understand the flow of your ideas better if you use parallel structures when you speak. Read the following incorrect example:

My teacher gave interesting assignments and motivating the students.

The listener may be confused because the speaker has mixed different grammatical structures. Does the speaker mean My teacher gave interesting and motivating assignments to the students'? In this sentence, interesting and motivating are parallel adjectives. Or does the speaker mean My teacher gave interesting assignments and motivated the students? In this sentence, gave and motivated are parallel verbs.

5. 对关键词进行替换或同义转换

When a speaker keeps repeating a word or phrase, listeners can get confused. Read the following example:

My teacher wrote the assignment on the chalkboard. The assignment was on the chalkboard until the teacher erased the assignment after we had all done the assignment.

This speaker's ideas would be clearer if the repeated words were replaced with other expressions or with pronouns. Look at the way this example can be improved:

My teacher wrote the assignment on the chalkboard. She erased the board after we had all completed the task.

The word assignment has been replaced with task; the word teacher with she; and the word chalkboard with board.

6. 时态、人称和数量的统一

Your listener can get confused if you are not consistent. Look at the following example:

My teacher brought five paper bags to school one day. He put us into groups and gave each group a bag. You have to take the objects out of the bags in turn and then a person has to tell a story involving the object from the bag.

The listener may get confused by the change from the past tense to the present tense, and the change from us to you and then to a person. The listener might also be confused by the change from the plural form objects and bags to the singular forms object and bag.
The listener could follow this speaker's ideas better if the speaker were consistent. Look at the way this example can be improved:

One day my teacher put us into five different groups. He gave each group a bag and told us to take turns pulling out an object and telling the other members of the group a story involving that object.