Lac genes are most effectively expressed in presence of Lactose and its analogs when glucose is absent.
Explanation:
A unit of prokaryotic gene expression and regulation,which includes structural genes and regulatory sequences recognized by regulatory gene product is called operon. 
<em>Lac </em>structural genes are a part of<em> Lac</em> operon. The <em>Lac </em>operon consists of three, structural genes,an operator and a promoter.The product of Lac operon is involved in the conversion of disaccharide lactose into glucose and Galactose.
Lactose and its analogs are inducers of<em> Lac </em>operon. So, the structural genes are best expressed in presence of Lactose. Glucose and galactose are repressors of lac gene so the genes are repressed in presence of glucose.
 
        
             
        
        
        
Answer:
DNA
Explanation:
RNA is not a double helix
Uracil is on the RNA, this is a picture or DNA. Uracil is just one of the nucleic bases
This is not a monomer; it's actually a polymer
It is DNA because it is a double helix structure held together by the four nucleic bases.
 
        
             
        
        
        
Answer:
Giraffes usually only have a single baby, born after a 15-month gestation period. But because they're able to breed all year round, giraffes don't need to 'resynchronise' with the seasons each time they give birth. Sadly, about 50% of giraffe calves do not survive their first year.
Explanation:
Hope this will help
 
        
             
        
        
        
Parasitic.
you need to know each of these choices meaning so that it will be easier to solve such a problem.
parasitic means it consumes its host and leave it only exhausted adn maybe dead.
autotrophic is like plants, they can make their own food.
saprophytic means is called on an organism, especially fungi, that feeds on dead material only.