Answer:
An underground cavern collapsed 
Explanation:
I did research
 
        
             
        
        
        
Answer:
D. A cyanobacterium
Explanation:
Cyanobacteria have gas vacuoles, thykaloid membranes and carboxysomes
 
        
             
        
        
        
Answer:
C, a decrease in metabolic activity
Explanation:
In times of drought, there would be a reduction in the metabolic activity of an organism. 
- Most organisms found in very dry climates have adaptation to accommodate a period of drought. 
- Water is essential for the metabolic processes in an organism. 
- A deficiency of water will reduce these life activities. 
- The organism can become inactive as a result of this.