The correct option is B When the full amount has not been paid.
The seller of goods is deemed to be an "unpaid seller" within the meaning of this Act:
(a) When the whole of the price has not been paid or tendered.
(b) When a bill of exchange or other negotiable instrument has been received as conditional payment and the condition on which it was received has not been fulfilled by reason of the dishonour of the instrument or otherwise.