B. White petal colour is a recessive trait.
Explanation:
In Mendelian genetics, the alleles depicted in small letters are recessive traits.
Since both alleles are same and in lower case they are homozygous recessive alleles for a white coloured petal gene.
The genotype of the trait will be tt because if it is crossed either with heterozygous or homozygous P alleles it will appear as tt to have phenotypic trait of white colour.
 So the genotype will be tt.
 
        
                    
             
        
        
        
And: Facilitated diffusion is a type of passive transport that allows substances to cross membranes with the assistance of special transport proteins. Some molecules and ions such as glucose, sodium ions, and chloride ions are unable to pass through the phospholipid bilayer of cell membranes.
        
             
        
        
        
Im not positive but I think it's b or c
        
                    
             
        
        
        
Water diffusion is called osmosis. Oxygen is a small molecule and it's nonpolar, so it easily passes through a cell membrane. Carbon dioxide, the byproduct of cell respiration, is small enough to readily diffuse out of a cell. Small uncharged lipid molecules can pass through the lipid innards of the membrane.