Dysfunctional uterine bleeding (DUB) is caused by a. endometrial fibroid tumors. b. absent or diminished levels of progesterone. c. endometrial inflammation. d. reproductive tract malignancies.

b. absent or diminished levels of progesterone

Explanation:

Dysfunctional uterine bleeding refers to abnormal uterine bleeding that causes the endometrial line to shred off in an abnormal manner.

Fibroid tumor, endometrial inflammation and malignancies are indirect causes of uterine bleeding but most common cause is the hormonal imbalance.

Progesterone is responsible for development and maintenance of endometrium so absent or diminished levels of progesterone is the cause of DUB.