The correct answer is: Only I and II are implicit.
The statement says that the government has asked the dealers to release a vast quantity of imported sugar in the open market. This implies that the government believes that this will help to bring down sugar prices. However, it is not certain that the dealers will follow the government directive. It is also possible that the release of imported sugar will not have a significant impact on sugar prices. The price of indigenous sugar may also remain unchanged, even if the price of imported sugar comes down.
Therefore, only assumptions I and II are implicit in the statement. Assumption III is not implicit, because the statement does not say anything about the price of indigenous sugar.