When Can the Collector Take Possession of the Land Under

When can the Collector take Possession of the Land under Acquisition process u/s 38?

A) after ensuring the full payment of compensation within the period of three months
B) after ensuring rehabilitation and resettlement entitlements are paid or tendered to the entitled persons within a period of six months for the monetary part of rehabilitation and resettlements.
C) after the publication of notification showing the intension to acquire
D) both (a) & (b)