The equation of standard normal distribution is f(z)=________?
A. 1/σ√2∏e 1/2×2
B. 1/σ√2∏e -1/2×2
C. 1/√2∏
D. 1/σ√2∏
A. 1/σ√2∏e 1/2×2
B. 1/σ√2∏e -1/2×2
C. 1/√2∏
D. 1/σ√2∏