After teaching a group of students about the types of urinary incontinence and possible causes, the instructor determines that the students have understood the material when they identify which of the following as a cause of stress incontinence?

a. Obstruction due to fecal impaction or enlarged prostateb. Bladder irritation related to urinary tract infectionsc. Increased urine production due to metabolic conditionsd. Decreased pelvic muscle tone due to multiple pregnancies