Can you tell me how many English words ____ since 1996?

I don’t know _____ he will come tomorrow. _____ he comes, I’ll tell you.

—I hear Sam has gone to Qingdao for his holiday.
--Oh, how nice! Do you know when he_______?

—I hear Sam has gone to Qingdao for his holiday.
 --Oh, how nice! Do you know when he_______?