I believe the answer is D. The atmosphere, different layers of the atmosphere can help in different ways! The stratosphere helps protect us from the sun's rays; The Mesophere is what helps protect us from meteorites! It's so cold that they burn up in that area.
The substance that releases the greatest amount of ions will have the greatest attractive forces within its solution, resulting in a reduced freezing point.
K₂SO₄ yields 3 ions
NH₄I yields 2 ions
CoCl₃ yields 4 ions
Freezing points:
CoCl₃ < K₂SO₄ < NH₄I
The efficiency of any machine is given by:
efficiency = output obtained / input given
Substituting the values,
Efficiency = 105 / 150
Efficiency = 0.7
Converting this to a percentage, the efficiency of the hammer is 70%.
This is a fairly high efficiency, and this is due to the fact that the hammer is a simpler machine. The more complex a machine is, the greater are the losses in it due to friction, meaning there is a lower efficiency.