Laboratory rats and mice live up to 40% longer than usual when fed a diet of at least 30% fewer calories than that which they would normally eat, but that otherwise contains all necessary vitamins and nutrients.

(a) of at least 30% fewer calories than that which they would normally eat, but that otherwise
(b) with at least 30% fewer calories than what they would normally eat though otherwise it
(c) that has at least 30% fewer of the calories than they would normally eat, but otherwise it
(d) that has at least 30% fewer calories than they would normally eat but that otherwise
(e) that has at least 30% fewer calories than that which they normally eat, though that otherwise