My sister whom you talked to last night lives in Canada. I will hold an activity that students will participate in. 兩句文法有錯嗎 另外that可省略嗎?

My sister whom you talked to stays in Canada last night. I will hold an activity in which students will participate.
live有居住一段時間，另時間副詞位置一般置於句尾。
第二句是較正式寫法

American English:
My sister whom you talked to last night lives in Canada.

British English:
My sister to whom you talked last night lives in Canada.


I will hold an activity that students will participate in.

1. You could replace the second "will" with other modal auxiliary verbs, for example, "can".

2.Yes, you could omit "that", or keep it in the sentence. Both are correct.

My sister (whom you talked to last night)---rel pron in defining /restrictive clauses.an independent relative also.
I will hold an activity(that students will participate in/about /)----rel pron in defining clause or restrictive clauses is not replaceable by whom; clause set off by the use on adjacent placing in defining the subject