Actually, they're not.  There's a group of stars and constellations arranged 
around the pole of the sky that's visible at any time of any dark, clear night, 
all year around.  And any star or constellation in the rest of the sky is visible 
for roughly 11 out of every 12 months ... at SOME time of the night.  
Constellations appear to change drastically from one season to the next, 
and even from one month to the next, only if you do your stargazing around 
the same time every night.
Why does the night sky change at various times of the year ?  Here's how to 
think about it:
The Earth spins once a day. You spin along with the Earth, and your clock is 
built to follow the sun . "Noon" is the time when the sun is directly over your 
head, and "Midnight" is the time when the sun is directly beneath your feet.
Let's say that you go out and look at the stars tonight at midnight, when you're 
facing directly away from the sun.
In 6 months from now, when you and the Earth are halfway around on the other 
side of the sun, where are those same stars ?  Now they're straight in the 
direction of the sun.  So they're directly overhead at Noon, not at Midnight.
THAT's why stars and constellations appear to be in a different part of the sky, 
at the same time of night on different dates.
        
                    
             
        
        
        
Average speed is worked out from dividing distance by time.
        
                    
             
        
        
        
Answer:
single replacement
Explanation:
In the question it says one element replaces another element which means there is only one replacement.
 
        
             
        
        
        
I would say that strong language typically reveals strong feelings: strong language would reveal desperation, or very strong feelings: weak feelings would not demand it, and would be more likely accompanied by more controlled behavior. 
        
                    
             
        
        
        
Physical change = changes the physical properties (more commonly known as it's look)
Chemical change = changes the chemical properties into an entire new chemical form
Examples of physical change would be melting ice cubes or sugar cubes.
Examples of chemical change would be cooking eggs or burning paper because you're changing its chemical properties.