Which statement correctly describes a relationship between two human body systems?

Choices:
(a). The digestive system absorbs nutrients which are transported by the nervous system.;
(b). The digestive system absorbs nutrients which are transported by the circulatory system.;
(c). The circulatory system exchanges gases which are transported by the nervous system.;
(d). The circulatory system exchanges gases which are transported by the digestive system.;
(b).