18 Consider the following null hypothesis for returns: r_t=+r_{t-1}+t; _tiidN(0,^2) where || 0. Which of the following is correct ? Question 16Select one: a. Under the null, the multiperiod (log) return is staionary and not autocorrelated b. Under the null, the single period (log) return is not autocorrelated c. The Variance Ratio statistic is equal to one under the null d. The Variance Difference statistic is not equal to zero under the null e. Under the null, the single period (log) return is nonstationary