The initial volume in the cylinder is 20 ml
adding the rock adds volume to the cylinder
the new volume is 32 ml the increase in volume is the volume of the rock : 32 - 20 = 12 ml volume of rock
i think the answer is a, hope this is right, that would be my best guess.
b mirrors submit a iisner? e. for which optical devices does d sometimes have a positive value? o a a and b o b. a and c o c. b and d 0 d. b and cb