A 27-year-old has just had an ectopic pregnancy. Which of the following events would be most likely to predispose to ectopic pregnancy?
a. Previous tubal surgery
b. Pelvic inflammatory disease (PID)
c. Use of a contraceptive uterine device (IUD)
d. Induction of ovulation
e. Exposure in utero to diethylstilbestrol (DES)