Answer: The correct answer is - 
b. Threshold. 
Explanation:
Threshold can be described as minimum voltage of a memrane (of neuron or muscle cell) that is required to reach an excited state of cell during a depolarization) so as to produce an action potential. 
Voltage-gated channels are activated at the threshold voltage, .
For example - Threshold level of neuron is - 55mV, which means it fires action potential at this level so that information is transferred to another neuron. 
 
        
             
        
        
        
Answer:
Eat healthy and get regular exercise. 
Maintain a healthy body weight.
Don't abuse drugs or alcohol and practice safe sex 
Extra:
Protect your skin (especially from the sun)
Base your diet on plenty of foods rich in carbohydrates.
Reduce salt and sugar intake.
Eat regularly, control the portion size.
Drink plenty of fluids.
<em>Any of these will work :)</em>
 
        
             
        
        
        
The answer is D. Chordata.
There are three domains of life - Archaea, Bacteria, and
Eukarya. All organisms that belong to the domains Archaea or
Bacteria have cell walls. In the domain Eukarya, there are some groups
that have cell walls and others that do not.
Chordata is phylum of the kingdom Animalia which belongs to the domain Eukarya. So, Chordata cannot be a domain.