HE HAD BEEN TEACHING SINCE TWENTY-FIVE YEARS BEFORE HE RETIRED LAST...
9. He had been teaching since twenty-five years before he retired last year.
a. had been teaching
b. since
c. before
d. retired
--> b
9. He had been teaching since twenty-five years before he retired last year.
a. had been teaching
b. since
c. before
d. retired
--> b