Erica purchased adult and youth tickets for a movie. She bought x adult tickets for $7 each and y youth tickets for $5. Write an expression that can be used to show the total cost, C, of all tickets.
A. C = 7x + 5y
B. C = (7 + 5)x
C. C = (7 + 5)(x + y)
D. C = 7y + 5x