我矿主井由井口至井底板，共计深340米。

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