单项选择题

若在[0,1]上有f(0)=g(0)=0,f(1)=g(1)=a>0,且f"(x)>0,g"(x)<0,则的大小关系是()

A.I1≥I2≥I3
B.I3≥I2≥I1
C.I2≥I3≥I1
D.I2≥I1≥I3