The correct order of reactivity in nucleophilic substitution reaction of the following compounds a, b, and c would be, where (a) is $$CH_3CH_2CONH_2$$, (b) is $$CH_3CH_2COOCH_3$$ and (c) is $$CH_3CH_2COCl$$

A

$$a > c > b$$

B

$$a > b > c$$

C

$$c > b > a$$

D

$$c > a > b$$