Answer :
C.
The yellow costumes will be 1 part out of a total of 3 parts, or 1/3, and the blue costumes will be 2 parts out of a total of 3 parts, or 2/3.
The yellow costumes will be 1 part out of a total of 3 parts, or 1/3, and the blue costumes will be 2 parts out of a total of 3 parts, or 2/3.