Only iodine forms hepta-fluoride $IF_7$,but chlorine and bromine give penta-fluorides. The reason for this is:

• A
  low electron affinity of iodine
• B
  unusual pentagonal bipyramidal structure of $IF_7$
• C
  that the larger iodine atom can accommodate more number of smaller fluorine atoms around it
• D
  low chemical reactivity of $IF_7$