When foreign learners study in free Chinese lesson, they often meet the reading exercises that to explain the complicated words with the simple ones have the similar meaning after reading some sentences. For the sentence 很难说王建的决定有什么特别动机, learners should know动机means the motivation of doing certain things. So students in free Chinese lesson can understand it as purpose and explain with the word 目的. The word 成心 in the sentence 你这不是成心跟我过不去吗 indicates doing something on purpose, so we can explain with 故意.

The word 圆满 is one of the important words when you learn Chinese words. In the sentence 他圆满完成领导布置的任务, it carries the meaning of realizing something successfully, which can be replaced by 成功. When you meet the sentence 这个结果对他来说未必不是件好事 in free Chinese lesson, you should know 未必implies some kind of uncertain meaning. So we can say 不一定.