If only the letter ___________ there in time!

If only the letter ___________ there in time!
A、arrive
B、is arriving
C、had arrived
D、has arrived
【正确答案】：C
【题目解析】：句意：那封信要是及时送到那里就好了!  if only意为”要是......就好了“，本题考查虚拟语气。