题目

A Harvard research team’s first model of a portable exosuit (机械护甲) is made of cloth components worn on the waist and upper legs. A computer that’s built into the shorts can sense when the user shifts between walking and running. Say the word exosuit and super heroes come to mind — somebody like Tony Stark from Marvel Comics, whose fancy suit enables him to become Iron Man. But scientists at Harvard University have been developing an actual exosuit, a wearable machine that can improve an average man’s strength and toughness. This model improves a wearer’s performance while he I don't have classes ________ Sundays and Saturdays.A.inB.atC.onD.of