The answer would be B. Atom, star, galaxy, universe. 
Explanation: atoms are small cells that make up everything in existence. They're too small to be seen by the naked human eye. Stars are big balls of gas that can be seen at night in the sky. These are second biggest because you can see these with the naked eye, but galaxies you can not. The galaxy holds the earth, all of the other planets, stars, and other things. If the galaxy can hold all of that then clearly it would be bigger than the stars. The universe is what holds our galaxy. There are millions of other galaxies out there in the universe. Ours is just a small one of an infinite number.
        
             
        
        
        
Answer:
The cuticle is the hair's protective layer, the cortex forms the pigment of the hair, the health of the cortex depends on the cuticle protecting it while the medulla is the innermost of the hair.
Explanation:
The cuticle is the hair outermost layer, the cortex is the middle structure for strength while medulla is the inner most.
 
        
             
        
        
        
Two or more organs form together make organ systems.
<u>Explanation:</u>
The basic unit of living organisms is the cell. Multiple cells makes up tissues and tissues make up organs. Two or more organs make up the organ system.
Human body has several organ systems. The organs that make up an organ system can be internal as well as external. Respiratory  system is made up of organs like lungs, nose, pharynx, trachea, diaphragm etc. digestive system is made with organs like liver, small intestine, stomach, mouth , large intestine, pancreas etc.