When designing for a specific client, you should consider:

a
their personality
b
the function of the design
c
the formality of the occasion you are designing for
d
all of the above

D. All of the above

Explanation:

You should consider their personal style and how much skin they would want to show at their certain event, the function of the design for reasons of how long they could be at their event and how the outfit should fit, and the formality of the event for reasons such as attire, you wouldn't want to design a ball gown for an event with cocktail chic attire.

I hope this helps :)