Grade 6 aural part A

I have a very low bass voice but I know that the grade 6 aural which I will be doing in Oct 2018 needs me to sing the upper part in part A. I know that in part B sight singing I can choose to sing in bass clef, but I'm afraid that I cannot reach most of the notes as they are all written in treble clef and my vocal range can only go up to D4. So should I use falsetto in that part or should I sing -8va?