<span>There are four possible phenotypes with a dihybrid testcross. The 1:1:1:1 ratio means that there is an equal chance of any of the four expected phenotypes in the offspring.</span>
        
             
        
        
        
It was not until the year of 1952!
        
             
        
        
        
Answer: C) Apical
Explanation: An epithelium has a free surface, the apical surface, exposed to the outside, and an attached surface, the basal surface, resting on the underlying connective tissue.