A) A flap in the heart located between each atrium and ventricle.
Hope it helps! :)
        
                    
             
        
        
        
Earth is always rotating around the sun that means if it were winter on one side of the world, (that is not on the side of the sun) the other side of the world would be summer, ( the side that the sun is shining on)
        
             
        
        
        
Science can only explain logical questions and provide answers to things that only can be scientifically proven. Things that are asked in society like religion can not be further explained. The reason why we have religion is because we have always believed in something in history. Either is was made up or concocted out of no where, humans have always believed in something. But what science can't explain is the miracles and things that have happened. Like Jesus, they can't prove that he performed miracles or was the Son of God. They can't prove he and his body ascended into heaven. Science can't explain that God is real. Yet the only thing you can do is believe in it, and trust the Bible accounts are accurately true.
        
             
        
        
        
Answer:
Invertebrates are the organisms in which backbone or vertebral column is absent. 
The three macroinvertebrate categories are annelids, mollusks and arthropods. 
Annelids are the organisms having segmented body. They are found in moist places. Examples are leeches and earth worms. 
Mollusks are the organisms which are enclosed in a calcium carbonate shell. Examples are snails and slugs. 
arthropods are the invertebrates which have segmented body and jointed appendages. Examples are insects and crustaceans etc.