Can anyone point out why (I know the correct answer but don't know why) I am wrong?

Problem 3, Part 3 of 4 0.25/1.0 point (ungraded) 11 a = {1: "Face", 2: "Beans", 3: "Pants, 4: "Loaf"} 21 b = a 31 a[5] = "Straw" 4 b[4] = "Geese" 5 a[4] = "Couch" 6 b[6] = "Trot" What is the value of b[4] when the code above is done running? If an error will arise on any of those lines, enter "Error" (without the quotation marks). If there is no b[4], enter "None" (without the quotation marks). Geese X What is the value of b[5] when the code above is done running? If an error will arise on any of those lines, enter "Error" (without the quotation marks). If there is no b[5], enter "None" (without the quotation marks). None x What is the value of a[5] when the code above is done running? If an error will arise on any of those lines, enter "Error" (without the quotation marks). If there is no a[5], enter "None" (without the quotation marks). Straw What is the value of a[6] when the code above is done running? If an error will arise on any of those lines, enter "Error" (without the quotation marks). If there is no a[6], enter "None" (without the quotation marks). None x