Individuals who are heterozygous for the sickle-cell allele suffer less from the attack of malaria because a small percentage of the red blood cells are sickle-shaped. They are more resistant to malaria than individuals who have two copies of the normal haemoglobin allele. Heterozygous individuals have a better chance of surviving and reproducing in regions where malaria is prevalent since they do not fully contract the disease.
        
             
        
        
        
Reproductive strategy is loosely used to refer to the way an animal mates and/or raises offspring
        
             
        
        
        
Lean women with a BMI less than 20 have an increased risks of preterm delivery, and deliver- ing a low-birth weight infant. The correct option among all the options that are given in the question is the first option or option "a". Similarly it is not good to gain excess weight while in the pregnancy stage, as the baby might grow at a larger proportion that required. 
        
                    
             
        
        
        
The correct answer is none of the above. 
Bacterial cells can transfer genetic material through a process called bacterial conjugation. This process involves the direct physical contact of the bacterial cells and a horizontal gene transfer. The genes which are transferred are most of the times beneficial for the recipient, such as genes for antibiotic resistance.
In this example, bacterial cells cannot have physical contact, since they are separated by a glass filter. Therefore, the bacterial conjugation cannot happen. Given that no gene transfer can be achieved, the AY strain remains bio- trp- and is unable to grow on any medium that lacks bio or/and trp.