Answer:
A. The fern transitioned from gametophyte generation to sporophyte generation. 
Explanation:
Ferns undergo an ALTERNATION of GENERATIONS in their reproductive life cycle. That is, they alternate between an incospicuous gametophytic stage and a dominant sporophytic stage. The sporophyte produces haploid spores, which germinates into the gametophyte plant called PROTHALLUS. 
The gametophyte produces gametes (male and female) which fuse together to form the diploid zygote, which eventually develops into the SPOROPHYTE plant via mitosis. In this question, the brown dots from the underside of a fern's leaves that Maria collected are the spores. 
When she places them in a pot, the spores germinated into gametophyte stage, then formed sporophyte, which is the small leaves she noticed growing from the pot. From this, it can be observed that the fern is transitioning from GAMETOPHYTE generation to SPOROPHYTE generation. 
 
        
                    
             
        
        
        
Tissues
Tissues are somewhat more complex units than cells. By definition, a tissue is an organization of a great many similar cells with varying amounts and kinds of nonliving, intercellular substance between them.
 
        
        
        
Prokaryotes do not have membrane bound organelles, but eukaryotes do.
        
             
        
        
        
Explanation:
In the process of photosynthesis, plants that contain chlorophyll utilize carbon dioxide and water using energy from sunlight that is absorbed by chlorophyll to make glucose + oxygen.