| In this paper, we solve Ahsan's problem provided in [3], that is ,whether the characterization of commutative regular ring as each submodule of quasi-flat module is quasi-flat is true in the noncommutative case. In §3, we proved that Th3.1. Let R is commutative ring, then R is regular ring iff every quasi-flat module is flat. As a consequently, if R is commutative ring, then R is regular ring iff R is generalized QI-ring ([3,Th.3.11, Th.3.4]); if R is left self-injective ring, then R is regular ring iff every left quasi-injective module is fp-injective. |
