a) is wrong since we haven't got the following structure in English has had give
c) the same goes for this answer. Has been give is wrong
b) is a bit vague if I may say so. Was/were to do sth does not imply whether the action was performed or not. Reading the whole sentence provided by you it is obvious that first he had to give up his work, which he really did, and than he started law school.
d) this is the only possibility left.
Student or Learner