Within a gymnosperm megasporangium, the following developmental sequences that are correct, assuming fertilization occurs is: megaspore, female gametophyte, egg cell, sporophyte embryo. The last Option (Option D) is correct.
In gymnosperm megasporangium, the meiotic division produces four haploid megaspores from a single cell, three of which generally degenerate. The female gametophyte is formed by mitosis from the surviving megaspore. 
Prior to fertilization, the male mature gametophyte needs to be transferred to the female gametophyte for fertilization to take place.
When the nuclei of the sperm encounter the nucleus of the egg cell in gymnosperms, it fuses with the egg nucleus to produce a diploid zygote. 
Mitosis occurs in the fertilized egg to initiate the growth of a new sporophyte generation (the multicellular embryo of the seed.)
Therefore, we can conclude that we've understood the mechanism of developmental sequence in the gymnosperm megasporangium. 
Learn more about the gymnosperm here:
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Answer:
Metabolism!! 
Not to mention pretty much the entire digestive tract and nervous system.
Explanation:
 
        
                    
             
        
        
        
Water pollution occurs when a body of water is adversely affected due to the addiction of large amounts of materials to the water.
        
             
        
        
        
Answer:mitosis
Explanation:meiosis produces haploid gametes. Mitosis is simple cell division
 
        
             
        
        
        
Answer:
The central part of the atom, composed of protons and neutrons.