Question

do you still remember the day ____you joined the Army and _____we spent together? 请填空 再解释一下

Answer 1

when.......which/that
and 在这里连接两个并列的定语从句。定语从句连接词的选择不仅要看先行词，更要看它在从句中所担任的成分。
第一个从句中主语（you）谓语（ joined ）宾语（the Army ）都有了，故关系词在从句中担任状语，先行词the day 表示时间，要用when;
第二个从句中spent后没有宾语，所以关系词在从句中做宾语，用which/that
（We spent the day together.)

Answer 2

when that
you joined the Army (in the day) 做状语
we spend (the day) together 做宾语

Answer 3

when 定语从句差状语
that/which spend sth. 定语从句差宾语

Answer 4

when that