4. The Cox proportional hazard model used to quantify the unadjusted association is as follows: In (hazard of death at time t; x) = In (1,(t)) + 1.03x1 where x1 = 1 for children who received dialysis at for profit facilities, and 0 for children who received dialysis at for not-for-profit facilities. What does the function In (^,(t)) characterize? a. The In(hazard) of death for children who received dialysis at for not-for-profit facilities at time = 0 in the follow-up period. b. The In(hazard) of death for children who received dialysis at for for-profit facilities at time = 0 in the follow-up period. C. The In(hazard) of death for children who received dialysis at for not-for-profit facilities as a function of time across the follow-up period. d. The In(hazard) of death for children who received dialysis at for for-profit facilities as a function of time across the follow-up period.