Answer:
By researching, I would think that the answer is D. Ice crystals melt as they fall through a warm layer of air and then refreeze into small ice pellets as they pass through a colder layer of air.
Explanation:
<em>During precipitation formation, if temperatures are at or below freezing, 0°C (32°F), at cloud level, water in the air freezes into ice crystals, and the crystals stick together to make snow. The snow starts to fall, and if the air column is freezing cold all the way down from the clouds to the ground, the precipitation stays frozen. It simply falls as snow.</em>
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<em>Sometimes, however, a temperature inversion occurs. Normally, the temperature decreases with increasing altitude. A temperature inversion is when a layer of warm air intrudes between the ground and the clouds.</em>
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<em>Under these conditions, when the falling snow reaches the layer of warm air, it melts. Then it hits the layer of cold air just above Earth’s surface and refreezes. This all happens very fast, and the result is tiny ice pellets called sleet.</em>
 
        
             
        
        
        
I think the second option is the best (by making the ramps height and length equal) because the first option will require more pushing, the third option will only make the ramp lighter which could cause it to not stay in place, the last option would make it harder to push the boxes up because the rubber will make it harder to slide the boxes up. I hope this helps:)
        
             
        
        
        
Muscles are required in breathing, talking, running, walking, and any body movement. Actin and myosins are protein filaments present in muscle cells that help to contract and relax or change the shape of muscles. Muscles are responsible for the movement or motion of organisms. Joints are the connection between two or more bones. Most joints are mobile.
Muscle strength is determined by several factors. Some of those are the physical shape, size, and innervation of the muscles.  
Weak contraction
- Potassium accumulates in the sarcoplasm. 
- Contracted lower sarcoplasm pH.
- Begin contraction with muscle already 50%. 
- The circular arrangement of muscle fascicles. 
Stronger contraction 
- Increase in muscle belly circumference. 
- A lesser proportion of motor neurons to muscle fibers. 
- Increased recruitment. 
- Increased stimulus frequency.