Answer:
 (a) can be used to bend epithelial sheets into tubes.
Explanation:
The adherens junctions are cell-cell adhesions localized in places exposed to abrasion or mechanical stress, close to the apical membrane in epithelial cells is one of these locations. Some of their functions are the initiation and stabilization of cell-cell adhesion, <em>they join the actin cytoskeleton to the plasma membrane to form adhesive contacts between cells that contribute to the folding and bending of epithelial sheets,</em> therefore they can mediate adhesion and signaling. 
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Sebum, a fatty substance that serves as a water repellent it also serves as a natural antibacterial and antifungal agent, 
yes the skin is important not only to excrete but its also a protective organ that absorbs oxygen and nitrogen
        
             
        
        
        
Answer:
Continental crust is typically 40 km (25 miles) thick, while oceanic crust is much thinner, averaging about 6 km (4 miles) in thickness. The effect of the different densities of lithospheric rock can be seen in the different average elevations of continental and oceanic crust.
Explanation:
 
        
                    
             
        
        
        
Answer:
D. Ultraviolet rays from the sun are prevented from reaching Earth.
surface.
Explanation:
What little is known is that the Earth's magnetic field creates the so-called "magnetic shield" that provides protection against some other dangerous forms of radiation, namely cosmic rays and solar wind. 
While there is no danger of losing the Earth's gravitational field, the Earth's magnetic field is declining faster than any other geophysical phenomenon. This continuous loss of the Earth's magnetic field, and the associated increase in harmful radiation, are beyond human control.