My teacher gave interesting assignments and motivating the students.
很顯然，這屬於混用語法結構的一個典型錯誤。這會使句子產生歧義：難道是說My teacher gave interesting and motivating assignments to the students? 因爲本句中 interesting和motivating 是平行結構. 或者是My teacher gave interesting assignments and motivated the students? 因爲亦可以理解成gave和 motivated是平行結構.所以錯誤使用語法會帶來許多意想不到的麻煩。
當我們重複使用一個短語或單詞的.時候，不僅會給人以詞彙量過小的感覺，有時甚至也會造成誤解。我們來看一個例子：
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.事實上這句話的觀點會更加清晰，如果我們將重複的詞替換爲其他表達的話。我們再來看看改進後的表達：
My teacher wrote the assignment on the chalkboard. She erased the board after we had all completed the task.
其中 assignment 被替換爲 task; teacher 變爲了she; chalkboard 被改爲了board. 不但句子顯得更加生動活潑不刻板，信息量也比原來要多了。
多次強調過，在說口語時千萬要注意時態、人稱和數量的統一，而這些oral slips卻是中國學生最容易出現的問題。同時，這些問題會讓你的聽衆們糊塗，不明白你究竟要表達哪種意思。看一個例子：
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.
前面是一般過去時，後面突然轉爲現在時;同時人稱也由我們變爲你最後是一個他。最後單復的變化亦會令人很費解。估計考官們很難跟得上這種跳躍的思維，所以保持前後一致性很重要。我們來看改後的版本：
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.