That would be A. 
Most antibiotics that are used for gram positive bacteria target the peptidoglycan cell wall, but the ones for gram negative bacteria are more advanced and specific and target the cell membrane and alter the cell’s function(processes of proteins and dna/gene expression).
        
             
        
        
        
Octopus<span> muscle fibers run in all directions; when contracted, they form a "skeletal" support system.</span>
        
             
        
        
        
Answer:
Carbon-14
Source: "Carbon-14 dating is a way of determining the age of certain archaeological artifacts of a biological origin up to about 50,000 years old. It is used in dating things such as bone, cloth, wood and plant fibers that were created in the relatively recent past by human activities.
" (HowStuffWorks)
 
        
             
        
        
        
It is called ELECTRODE. 
When performing electrotherapy procedure, the electrode, which is an apparatus of current conductor is used to direct the current from the  appliance to the patient's skin. 
Electrotherapy procedure involves the use of electrical energy for medical treatment.