a) Unlike German shepherds or Doberman pinchers, there is an unwillingness on the part of many people to believe that pit bulls might be fully domesticated
Compares GS & DB with unwillingness.b) Many people, willing to believe that German shepherds and Doberman pinchers might be fully domesticated, are unwilling to believe the same of pit bulls.
Concise and remove the Dependent clause in between. The sentence reads just fine.c) Unlike German shepherds or Doberman pinchers, pit bulls bring out an unwillingness in many people to believe that they might be fully domesticated.
Comparison is good but pit bulls do not bring out any thing as per the Original sentence.d) Many people are unwilling to believe that pit bulls might be fully domesticated even while they are willing to believe that German shepherds and Doberman pinchers might be.
I am not aware of whether while is almost always wrong on GMAT. But sure does have issues with conciseness and claritye) Unlike German shepherds and Doberman pinchers, which many people are willing to believe can be fully domesticated, such belief does not extend to pit bulls.
Wrong comparsion