In which of the following situations is the most work done on the object?
a. holding a 50 kg object.
b. carrying a 30 kg object down a 40 m long hallway.
c. lifting a 20 kg object 1 m up.
d. carrying a 15 kg object up a flight of stairs.
e. lowering a 25 kg object from a second story balcony to the ground

Maybe c? sorry if im wrong

Yuauhahahanqqnnqhahajna

The correct answer is  "c".  it is "c" because melting is an endothermic change, and endothermic get's energy from surroundings. 

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.