I think it might be the first one: hiv infections. (hope this helps!)
        
                    
             
        
        
        
Directional selection I'm pretty sure hope it helps!
        
                    
             
        
        
        
Answer:
(c) G1 cyclins will be expressed during the S phase
Explanation:
In those cases in which G cyclins are constitutively expressed, the G1 phase will be shortened
 
        
             
        
        
        
Answer: overpopulation of predators
Explanation: Overpopulation of predators is the correct option. Predators are the organisms which kill other organism so as to obtain them as food. The organism being killed is called as the prey.
If the population of the predators increase this will lead to the extinction of many species of prey. As it is evident that every organism in the ecosystem has a typical role to play. Therefore, it can be said that role of prey will not be performed and this may lead to disturbance in the ecological balance.