What is a difference between prokaryotic and eukaryotic cells? A.
Eukaryotic cells do not have membrane-bound organelles, but prokaryotic cells do.
B.
Prokaryotic cells do not have a nucleus, but eukaryotic cells do.
C.
Organisms with eukaryotic cells are always multicellular, but organisms with prokaryotic cells are not.
D.
Prokaryotic cells always have cell walls, but eukaryotic cells do not.

B. Prokaryotic cells do not have a nucleus, but eukaryotic cells do.

Explanation:

in the cells of bacteria , cyanobacteria and mycoplasma,no nucleus is seen. these organisms are called prokaryotes .

but in the cells of amoeba ,animals and plants a well defined nucleus covered by membrane is seen. these organisms are called eukaryotes

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the unequal cytoplasmic division that  results  in  one egg  and three polar bodies ensures that a fertilized  egg has  ample nutrients  forits journey  to  the uterus.

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.