有關英文時態問題一問

If you are Tom;"I have received Mary's letter=were delivered"
Mary's letter went astray since.
Therefore, present perfect tense denotes present result of past action. The word "since " is used.

2014-10-08 19:41:16 補充：
When two actions happened in the past one after another, we use the (past perfect) tense for the first action.eg:-After I had received Mary's letter, I lost it.We use the past perfect tense if factors of completion on time are involved.

Jenkin 說得有理～

請對自己更有信心。

閣下時常設定一些複雜的處境情節，但提出的英文句子卻只有一個意思/動詞的句子，並期望個動詞的時態便可以表達你背後的假設(設定)情況，這有點誤會了時態或動詞句子的寫作法。

你現提出的內容其實有兩個時空的場景或情況，先是你(估"你"是tom是句子的"I"?)曾經收過信，...又估你是指過了一些時間後的"現在"唔見咗那封信。這情況"收信"是一個處境動詞，"唔見了"是另一個時空的處境動詞，要寫齊才能表達你想像中的意思，不是單單have received就可以。留意當有兩個相對/互有關係的時空處境時，時間的先後便要透過動詞的時態來告訴讀者，由於你想講"先收到信"，"後唔見咗"...兩個時空在當時來講其實都係perfect tense(剛完成)，所以先發生的便用past perfect tense來區分：

I had received a letter from Mary, but I have lost it.

希望你能全面一點地學習運用句式結構是用來表達意思，不是考試填充格格一個答案。