D 2:1, because a dime is worth twice as much as a nickel
Because the question has number of nickels listed first in the ratio that makes the answer 2:1 as opposed to B 1:2. Also, two nickels equal the same amount as one dime so for every two nickels there is one dime. In this case, there are 728 nickels and 364 dimes. 728/364 = 2/1 (simplifies down to the fourth ratio given)