Which of the following committee recommended two-tier Panchayatiraj institutions ?

The Ashok Mehta Committee (1977-78) recommended replacing the three-tier Panchayati Raj structure with a two-tier one: a Zila Parishad at the district level and Mandal Panchayats below it. The G.V.K. Rao Committee (1985) and the L.M. Singhvi Committee (1986) dealt with strengthening Panchayati Raj but did not propose the two-tier pattern.