下面哪个调度是串行调度( )

下面哪个调度是串行调度( )

A.T1:R(A),T2:R(B),T2:W(B),T1:W(A)

B.T1:R(B),T1:W(B),T2:R(A), T2:W(A)

C.T1:R(A),T2:R(B),.T1:W(A),T2:W(B)

D.T2:R(A),T1:R(B),.T1:W(A),T2:W(B)

正确答案是B