Answer:
B. Developed out of efforts of man trying to explain our physical environment.
Explanation:
 This is because physics, as we all know of, is considered to be <em>crucial to understanding the world around us</em>, making it the most basic and fundamental of science.
 
        
                    
             
        
        
        
Answer:
An instrument for measuring the density of liquids.
Explanation:
A hydrometer is an instrument used to determine specific gravity. It operates based on the Archimedes principle that a solid body displaces its own weight within a liquid in which it floats. Hydrometers can be divided into two general classes: liquids heavier than water and liquids lighter than water.
 Thermohydrometers is one type of hydrometer.
 
        
             
        
        
        
Using a lever to move a rock reduces the force a person must exert . It also reduces the work (effort ) the person must do.
Using a lever decreases the input force required to lift up the load, for example if a force of 900N is required to lift the load without a lever . Using the lever the input force decreases to 500N and as we all know by the formulae of work done :
Work done ∝  force applied 
By this equation we can conclude that if the force to be applied on the load reduces by the use of a lever therefore the work to be done on the load will also reduce .
You can get a additional information about the lever system below :
brainly.com/question/3522307
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