Consider your reasons for asking questions about sex/gender in any survey or form, since such questions may be problematic for people with a trans identity. There may be a justifiable need to ask questions about gender, such as for monitoring take-up of services.
National guidance on data collection in higher education has changed, with a move towards recognising a gender spectrum by offering multiple options of ‘male’, ‘female’ , 'non-binary' or ‘other’. It is also good practice to offer a ‘prefer not to say’ option, and you may wish to allow individuals to specify their gender identity in a free text field if they select 'other'.