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