Why do sex-linked traits follow different patterns of inheritance than other traits?
a. females can have a recessive trait with only one recessive allele.
b. males and females have different sex chromosomes.
c. males have two x chromosomes, and females only have one.
d. females do not carry alleles for sex-linked traits.

  sex-linked traits follow different patterns of inheritance than other traits because Males and females have different sex chromosomes 
so B is the right option 
 option C is wrong as it is females with two X chromosomes, and males who are XY.
A and D are wrong as well because 
females definitely carry alleles for X linked traits. If the allele on one X is recessive and the allele on the other X is dominant, they will express the trait for which they have the dominant allele. So they won't always express a recessive phenotype.
hop it helps