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. 
 
        
                    
             
        
        
        
Dalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties. ... The first part of his theory states that all matter is made of atoms, which are indivisible. The second part of the theory says all atoms of a given element are identical in mass and properties.
        
             
        
        
        
They travel the way the wind is blowing and also towards the shoreline
        
             
        
        
        
Water will evaporate from any
water source and life forms. The answer is letter C. An application of heat
into water will cause the water to evaporate. This is because the
intermolecular forces of attraction of water can be broken by sufficient energy
application.
 
        
             
        
        
        
Answer:
Balances and Scales
A balance compares an object with a known mass to the object in question. One example of a balance is the triple beam balance. The standard unit of measure for mass is based on the metric system and is typically denoted as kilograms or grams.