Which of the following features is used to identify a male...

In male cockroach, the 9^th sternite bears a pair of small spine-like unjointed caudal or anal styles which are absent in female cockroach. The anal styles are believed to function as a motion detector.
Besides this, the other three characters, i.e. anal cerci, boat-shaped sternum on 9^th abdominal segment and forewings with darker tegmina which are found in both male and female cockroaches.