Dr Mukul Sangma on Tuesday took oath as the chief minister of Meghalaya, replacing veteran Congress leader D D Lapang, who quit as the Congress Legislative Party leader on Monday night after losing the support of 21 of the Congress' 28 Members of Legislative Assembly in the 60-member state assembly.Governor Ranjit Sekhar Musahary administered the oath of office to Dr Sangma and three other cabinet ministers at a ceremony held at the Raj Bhawan in Shillong today afternoon.