In a sickled red blood cell, what do the hemoglobin molecules do?

In a sickled red blood cell, what do the
  hemoglobin molecules do?
 
  a. repel each other
  b. stick together
  c. fracture and release their contents into the
  cytoplasm
  d. create holes in the cell membrane
  e. more than one of these

Question 2

In sickle cell anemia, what condition happens
  to the hemoglobin molecule that causes the red
  blood cell to sickle?
 
  a. a small part of it becomes hydrophobic
  b. a small part of it becomes hydrophilic
  c. a small part of it becomes polar
  d. a small part of it becomes negatively
  charged
  e. more than one of these happens