. Which of the following time series is probably stationary?\" a] U.S. GDP since 1904]\" h] Enrolh'nent of students in ECDN 3951 across fall and spring semesters\" c) [1.5. ination rates since 1WD\" d] Average 3M1 {body mass index] of Americans since 1900\" 14 . You have daily data on l{'ioogle stock prices, which you want to regress on Google's ad sales. What can you do to remove stationarity issues?\" {A} The data is already stationary, so you're good.\" {B} Add a linear time trend as a control.\" {C} Use seasonal dummy variables as controls.\" {D} Use differencing {replace Y with d? and X with AX)\" {E} There is nothing you can do. You're screwed.\" 14 14 y