Final answer:
Mrs. Nevin can use a length of fabric that is 4/7 yard (option B), as it is the only length greater than 1/2 yard and less than 5/8 yard.
Step-by-step explanation:
Mrs. Nevin needs a piece of fabric that is greater than 1/2 of a yard but less than 5/8 of a yard for a costume. To find a length that meets this requirement, we need to compare each option given to these two fractions.
Option A: 3/8 yard is less than 1/2 yard.
Option B: 4/7 yard is approximately 0.571 yards, which is greater than 1/2 yard and less than 5/8 yard (0.625).
Option C: 3/7 yard is approximately 0.429 yards, which is less than 1/2 yard.
Option D: 2/4 yard is equal to 1/2 yard, which does not meet the > 1/2 condition.
Therefore, the correct length of fabric that Mrs. Nevin can use is Option B: 4/7 yard.