Consider a four-point moving average filter defined by the equation \(y\left[ n \right]=\mathop{\sum }_{i=0}^{3}{{\alpha }_{i}}x\left[ n-i \right].\)The condition on the filter coefficients that results in a null at zero frequency is:

• A. α1 = α2 = 0; α0 = -α3
• B. α1 = α2 = 1; α0 = -α3
• C. α0 = α3 = 0; α1 = α2
• D. α1 = α2 = 0; α0 = α3