I am currently taking an online course (at a university in the US) in which once a week I am in the same virtual meeting room as two professors, one male and one female, with the same last name. I am unsure in how I should go about directly addressing one of them when I typically address all my professors as "Professor <lastname>" . As a second-year undergraduate student, I have been told it is inappropriate to address both professors by their first name if they have not stated this is okay (e.g. my past professors have typically said "you can call me <firstname>" on the first day of class). Additionally, when I took a course with one of these professors last year, I (and all other students) addressed them as "Professor <lastname>". If addressing them by first name is inappropriate in this context, how would I selectively address one when both professors are in the room?
With the exception of myself and another undergraduate, all other students in this course are graduate students, and address the professors on a first-name basis. So this has not a common cause of confusion in the course.