If Polaris were to go supernova today, no one currently on Earth ever know it happened because it would take 434 light years to reach the Earth
Explanation:
The Polaris or the North Star that we can see at the North Pole of the Earth in the night historically dates back to 434 years in the past. If the Polaris becomes a supernova or if it dies now, it will take 434 years in the future from now to know about it. 
This is simply because ‘one light year is the distance traveled by light in one year’. Hence currently, one cannot know about what happened to the Polaris supernova even if it happens now.
 
        
             
        
        
        
Answer:
Option (3)
Explanation:
Springs (hot springs) and geysers are formed when the water from the interior of the earth are ejected into the earth's surface. In simple words, these are formed in the region where the groundwater and the ground surface intersects with each other.
The water obtained from springs can be cold or hot. Those that produce hot water are termed as hot-spring. These hot springs and geysers indicates the occurrence of volcanic activity. This water becomes hot due to the interaction with the magma at certain depths below the ground surface.
The geysers are also a type of hot-springs which produces hot water.
Thus, the correct answer is an option (3).
 
        
                    
             
        
        
        
Answer:
A stationary front is depicted by an alternating red and blue line with a triangle on the blue portion and half-moon on the opposite side of the red portion of the line. A cold front (or warm front) that stops moving becomes a stationary front.
Explanation:
 
        
             
        
        
        
Essentially, a control variable is what is kept the same throughout the experiment, and it is not of primary concern in the experimental outcome. Any change in a control variable in an experiment would invalidate the correlation of dependent variables (DV) to the independent variable (IV), thus skewing the results.
 
        
             
        
        
        
DNA replication begins when something called Helicase (an enzyme) unwinds the helix structure of the DNA. It does this so that Primase can then come along and set down an RNA primer.