Step 1: D&C is an instrumental procedure that dilates the cervix and curettes the uterine cavity. Any condition where instrumentation can spread or worsen infection is a contraindication.
Step 2: Active pelvic inflammatory disease involves infection of the upper genital tract. Passing instruments through the cervix during acute PID can disseminate the infection upward and provoke peritonitis, so D&C is contraindicated. This makes option a correct.
Step 3: Indeed, upper-tract procedures like D&C, recent IUD insertion and therapeutic abortion are recognised risk factors that can precipitate or aggravate PID.
Step 4: Endometriosis (option b) is not a contraindication. Ectopic pregnancy (option c) is managed surgically or medically, and curettage may even be diagnostically used, so it is not the listed contraindication. Hence PID is the answer.