I'm almost 100% it is the first option
        
             
        
        
        
Well a theory is when a person comes up with something that they believe is to be true, and they work on projects and other things to show their thinking. theories won't always bee correct which helps us humans grow and come up with new ones
        
             
        
        
        
Answer: ACID
Explanation:on the Ph scale their is acids and bass' the loewer the Ph is hte higher the acid will be
 
        
             
        
        
        
Answer:
Neighboring cardiac muscle cells in the walls of heart chambers have specialized cell-to-cell contacts that electrically and mechanically link the cells together, permitting the immediate passage of muscle impulses. These cell-to-cell contacts are called <u>intercalated discs.</u>
Explanation:
Intercalated discs can be described as unique structures present between the cardiac muscles of the heart. The intercalated discs play a major role in making the cardiac muscles contract in a rhythm so that the heart can pump blood in a regular fashion and it hence regulates the effective functioning of the heart. The intercalated discs are the structures that join on cardiac muscle to another and is involved in the transmission of chemical messages between them. 
 
        
             
        
        
        
Answer:
C. <em>Clostridium</em> and <em>Bacillus</em>.
Explanation:
<em>Bacillus </em>and <em>Clostridium</em> are the gram-positive bacteria and form endospores. Endospores are the resistant dormant structures formed by some gram-positive bacteria. 
These bacteria form the endospores within their vegetative cells. The endospores are highly resistant to environmental stress conditions and make these bacterial genera the dangerous pathogens.