she said she ___ mr five letters in one month.a) has writtenb) will writec) had writtend) wrote

she said she ___ mr five letters in one month.a) has writtenb) will writec) had writtend) wrote
she said she ___ mr five letters in one month.
a) has written
b) will write
c) had written
d) wrote

she said she ___ mr five letters in one month.a) has writtenb) will writec) had writtend) wrote
C 因为in one month“在一个月中”~所以用完成时~
又因为是said~而write又是在said之前发生的~所以用过去完成时~

C
主句过去时，写信发生在说之前，过去的过去，典型的过去完成时

had written
过去的过去，过去完成时