Which of the following procedures is always equivalent to adding 5 given numbers and then dividing the sum by 5 ？（）
Ⅰ Multiplying the 5 numbers and then finding the 5 th root of the product.
Ⅱ Adding the 5 numbers, doubling the sum, and then moving the decimal point one place to the left.
Ⅲ Ordering the 5 numbers numerically and then selecting the middle number.
A．None
B．Ⅰonly
C．Ⅱonly
D．Ⅲonly
E．ⅠandⅢ