A:When did the recycling program start?
B:It hasn't started yet.
A:Ok,when does it start ?
B:Next week.
A:Do you know how much trash Americans throw away every day?
B:No.But I bet it's a lot.I guess that's why our city started a recycling program.
A:A lot of other cities have ,too.
想請問知識大大們,就前面的對話來看資源回收還沒開始,但是為什麼最後A的對話句中start要用started呢?謝謝。