詢問關於英文tense 的問題

"Mary used a Samsung mobile phone." - 句子本身無問題;
但因當中沒有提及"time",i.e. "when"(幾時發生), 句子顯得不太清楚。

(1)如果是單一句子:
需要加入「發生的時間」,令 "tense" 的採用更明確:-
e.g. Mary used a Samsung mobile phone yesterday.

(2)如果是"a paragraph" or "a passage":
則要看整段之間的時間關係,去決定 一句子應用什麽"tense"

e.g. Mary died this morning. She had been using a Samsung mobile phone.

因為" Mary had been using a Samsung mobile phone"先發生(用past perfect continuous tense)- -> 才到"Mary died this morning " (用past tense)

(1) Before her death, she had used Samsung.

(2)After she died 7am. Peter lifted her property of Samaung.

Had no problem lee.

'Mary used a Samsung mobile phone' is grammatically correct

but using 'Mary had been using a Samsung moblie phone' is better

because the sentence shows that something started in the past and continued up
until another time in the past (Mary died).

Hope that it helps :)