No one here has any doubt about the partnership at all. Almost every one here might have studied partnership and "Partnership Act 1932". For sure partnership is what you have said. Issue is only of "Joint Venture". If it were not in the options, every one might have ticked Partnership blindly. But now, as the question options were
a. Something
b. Partnership
c. Joint Venture
d. Public Limited company
e. B & C both
.
That's why the answer, as per my knowledge was option 'E'. If they had to keep the things simple, they might have not included the Joint venture and specially the option "e" that was b & c both.

__________________
Pakistan Zindabad