比较下列四种化合物的水解活性:a:CH3COOCH3b: CH3COOC2H5c: CH3COOCH(CH3)2d: CH3COOC (CH3)3,他们的活性大小顺序是()
·a>b>c>d
·a<b<c<d
·b<a<c<d
·d>b>c>a