Hi !!
If it's a woman you don't know, you are going to use "vous" de politesse (formal vous)
C- Continuez tout droit et tournez à droite.
A- Continue tout droit et tourne à droite ==> for a close friend, someone you know
B- Continues ..et tournes . => is grammatically incorrect
CONTINUER //TOURNER imperative
continue //tourne (tu)
continuons // tournons (nous)
continuez /// tournez (plural & formal 'vous/tu')