Cell wall because their has to be something protecting it.
        
             
        
        
        
Answer:
Water vapor
Explanation:
Water vapor is the gaseous phase of water. Combustion of 1 cubic meter of fuel in a solid fuel furnace produces 0.8 liters of water vapor. 
It can be produced by the evaporation of boiling water or the sublimation of ice. Water vapor is water in gaseous instead of liquid form. The water when it's boiling it doesn't disappear, it becomes gas,  ,
 
        
             
        
        
        
Because the heads are polar/hydrophilic so they will be attracted to the water which is also polar whereas the tails are non-polar/hydrophobic so they will avoid the water at all cost.
        
             
        
        
        
Answer:
Contour interval in  surveying is the vertical distance.
Explanation:
Normally there are different contour intervals for different maps.The size of the area considers the contour intervals. In each and every map on the right hand bottom side the contour interval is specified.Therefore a contour interval is difference in two elevation between the contour lines in a topographical map
 
        
             
        
        
        
The core of a star must react a temperature of 10,000,000 degree  Celsius for hydrogen fusion to begin
Explanation:
A star formed from a rotating cloud which is made up with completely with helium and hydrogen. The gravitational force pulls the cloud behind to collapse inward and due to this it shrinks and later it spins more and more quickly with the outer parts.
When the core and inner part become a rough spherical clump then it becomes disk. The star life cycles follow the patterns which is based on mostly on their initial mass.