Consider the following statements regarding ribosomes                                         

 a) Ribosomes are amembranous organelles which are found in every type of cell

 b) It consists of two subunits which unite during the time of protein synthesis.

c) In eukaryotic cells, they are also found attached to the endoplasmic reticulum

d) They are made up of r-RNA and proteins

e) The charge on ribosomes is negative

How many of the above statements are incorrect ?