Answer:
D. crystalline solid that conducts current under certain conditions
Explanation:
Semiconductors are crystalline solids that has the ability to conduct electrical currents but on certain conditions e.g heat. The conduction of semiconductors is less than that of conductors (metals) but more than insulators (nonmetals), hence, they are said to be intermediates of conductors and insulators in terms of electrical conductivity. 
Examples of semiconductors are silicon, boron, carbon, germanium, arsenic etc. 
 
        
             
        
        
        
Answer:
The frequency of the wave is 5.0Hz
Explanation:
The frequency of a wave is the number of oscillations or revolutions made in a second.
 
        
             
        
        
        
Answer:
More than 20% of the amazon has been destroyed, affects biodiversity.
Explanation:
- The biggest issues that the amazon is facing is the deforestation and it involves the clearing of land areas for logging, farming, and other land-use changes. 
- Effects that are seen are droughts, floods, destruction of habitats of flora and fauna along with the valuable services of the ecosystem.
- This leads to a decrease in the carrying capacity of the species and the decline of the essential resources that are necessary to survive.