Answer: 4
The mechanical advantage is the ratio of the force exerted by the object to the force applied to do work on it.
Here, Jeff tried to lift a rock weighing 600 pounds by wedging board under the rock. Jeff who weighs 150 pounds uses all his weight to exert force on lever and lift rock.
Mechanical advantage, 
Therefore, the mechanical advantage that lever provided to Jeff in lifting rock is 4.
When a red giant has insufficient mass it pretty much sheds its outer layer to leave the center core know as the white dwarf
I think its A let me know its wrong or not
Answer:
In most materials, as heat energy is absorbed, the density decreases. IF a certain object is heated, it might appear bigger than usual because it expands as the molecules inside moves faster than usual. However the mass of it stays the same while the density decreases.
