有關現在完成式問題問問大家

圖片參考：https://s.yimg.com/lo/api/res/1.2/ZQit8r6YM3UMER1bF6V.OQ--/YXBwaWQ9dHdhbnN3ZXJzO3E9ODU-/http://i.imgur.com/ZH9B85L.gif

時態無問題，人名用詞有問題。
（因為你是 Sammy，不是 Mary。）

看看時間線
早上九時：Sammy 到 Tom 的店舖購一輛價值 $60 的玩具車

　　稍後：Tom 寫下收了 $60 （不是賺了，因為未扣除成本）

下午一時：Tom 說 "Mary has paid $60 for a toy car."

句子所用的是 present perfect tense (現在完成式)。
你想強調的是：顧客是否已經付款。
因此，你用 has paid 去分辨直至現在「付款」這個動作已經完成。

如果把 Mary 改成 Sammy 後，
句子的意思是 "Sammy has (already) paid $60 for a toy car."

如果你不想作已經付款這個強調的話，你也可以考慮用 simple past tense (簡單過去式)，即 "Sammy paid $60 for a toy car (this morning)."

其實你不必太執著，可以給予自己多一點信心。
加油吧～


2014-08-19 21:07:06 補充：
補充問：
Mary 係八月十八日叫我cancel 個appointment，我係八月十九日上午cancel 個
appointment，咁我係八月十九日下午同Mary 講"I cancelled the appointment this morning."有無問題。

補充答：
絕對無問題，完全正確！
用 simple past tense 用得好好！

無問題!
form http://210.240.55.2/~t311/moe/engb5/b5grammar/b5perfect.htm

2014-08-28 20:46:15 補充：
http://210.240.55.2/~t311/moe/engb5/b5grammar/b5perfect.htm

The present perfect tense:-
The present perfect tense indicates an action took place in the past, is associated with the present idea of now and used for an action just concluded when the resulting state is still present,
eg:-(A)Tom said,"Mary has paid $60 for a toy car 4 hrs ago this morning."
The time line (9-13=4) hrs.
eg:-(B)Doris said to Mary,"I have cancelled the appointment about 6 hrs ago this morning."
With activities of appointment completed in the immediate past this morning, ago is often used.
The time line (10-16=6) hrs-->about 6 hrs.