... YOUR ADDRESS, WE WOULD HAVE WRITTEN TO YOU.A. HAD WE KNOWNB. I...

45. - 70 DE THI CHUNG CHI B TIENG ANH
70 DE THI CHUNG CHI B TIENG ANH

45. ... your address, we would have written to you.

a. Had we known

b. If we have known

c. We had known

d. If we did know

 a