选择:1.It's a day ＿＿students send cards or flowers to their teacher.A.who B.at C.when

选择:1.It's a day ＿＿students send cards or flowers to their teacher.A.who B.at C.when

c when 为时间状语从句

C when

C. it's a day 是时间的

c

It's a day when students send cards or flowers to their teacher.
选 C

选C, when在这里作状语，相当于on this day