Answer:
Option A
Explanation:
Thyroid is primarily caused by lack of iodine but there are other reasons as well that lead to increased size of the thyroid gland. Some of these reason is 
a) over- or underproduction of thyroid hormones
b) Nodules in the glans
Some times, due to overstimulation immune system itself attack the thyroid gland thereby producing excess thyroxine and hence causing  the thyroid to swell
Thus, Option A is correct
 
        
             
        
        
        
Answer:
D. as an arrangement of four chemical bases
Explanation:
Our DNA is made up of 4 chemical bases (adenine, thymine, guanine, cytosine).
 
        
                    
             
        
        
        
Answer: C
Explanation: the application of scientific knowledge for practical purposes, especially in industry
 
        
             
        
        
        
Explanation:
production of living organism from nom living matter is known as spontaneous generation.