Which of these represent ensemble averaging if N represents the number of identical quantities?

• A. ( frac{1}{N} int_N phi dN )
• B. (lim_{N } frac{ u20611}{N} int_N phi dN )
• C. ( frac{1}{N} sum_{i=1}^N phi_i )
• D. (lim_{N } frac{ u20611}{N} sum_{i=1}^N phi_i )