a question of past continuous

當在同一句子，兩個動作都用過去進行式時，就表示兩個動作同時發生，是平行動作，如：

　　．I was studying while he was making dinner.
．While Peter was reading, I was watching television.
　　．Were you listening while I was talking?
　　．Peter wasn't working, and I wasn't working either.
　　．They were eating dinner, discussing their plans, and having a good time.


希望幫到你！

If this is a complete sentence and there is no other conditional sentence in front. This is wrong.

Past continuous tense is used only if the whole story was written as past tense while there was some situation happening relative to another action.

Correct writing:

While Michelle, Susan's pen friend, was visiting Hong Kong, Susan showed her all the favourite shops in Central.

(visit) and (show) only indicate the verb to be used. It is wrong to have both in past continuous tense.

再加一點中文解釋，was visiting要用past continuous tense是因為到訪香港是一段時間內的事情，而帶她朋友去中環是一次，所以用法是相對而言在香港旅覽期間(past continuous)中的一樣動作(simple past)才會用上past continuous tense。