Which of the following is not an example of doing work?

a. holding a tray in the cafeteria line
b. picking up a box off the floor
c. raising a barbell over your head
d. pushing a box across the floor

i will give brainliest to the first person who answers if they get it right
plz

In a simplified model of the human eye, the aqueous and vitreous humors and the lens all have a refractive index of 1.40, and all the refraction occurs at the cornea, whose vertex is 2.60 cm from the retina. what should be the radius of curvature of the cornea such that the image of an object 40.0 cm from the cornea’s vertex is focused on the retina?