Answer: glutamate
Explanation: Given the cascade of events leading to ischemia-produced brain damage, it has been suggested that glutamate antagonists administered immediately after a stroke might reduce the subsequent development of brain damage.
 
        
             
        
        
        
Answer:
The correct answer is- photosynthesis
Explanation:
According to the endosymbiotic theory, an ancestral cell engulfed a cyanobacteria and lived in symbiotic association with that bacteria and over time this bacteria evolved into the chloroplast and the ancestral cell developed into plant cell.
So as cyanobacteria was the first aerobic cell that can evolve oxygen and can do photosynthesis to produce organic food so it could be concluded that the presence of endosymbiotic cyanobacteria provided a cell with the advantage of photosynthesis. 
 
        
             
        
        
        
Answer:
Because the trophozoites are unable to survive outside a host.
Explanation:
The term infectious is used for a disease or microorganism that can be transmitted from one organism to the other organism through the environment. If we look at the two forms of Giardia, we find that out of the two forms viz. cysts and trophozoites, only the cysts of Giardia have the ability to remain alive in the environment outside the host and thus they are able to be transmitted to the other organisms. On the other hand trophozoites are not able to survive in outside environment so there is no chance of transmission of trophozoites.