The correct answer is: Only I is implicit.
The statement is about the X passenger car manufacturing company announcing a sharp reduction in the prices of its luxury cars. The assumptions are:
I. There may be an increase in the sale of luxury cars of Company X.
II. The other such car manufacturers may also reduce their prices.
III. The competitor companies may not reduce their prices.
Assumption I is implicit because if the prices of luxury cars are reduced, then there is a possibility that more people will buy them. This is because the cars will now be more affordable.
Assumption II is not implicit because there is no guarantee that the other car manufacturers will reduce their prices just because X has reduced its prices. They may choose to keep their prices the same or even increase them.
Assumption III is also not implicit because there is no guarantee that the competitor companies will not reduce their prices. They may choose to reduce their prices in order to compete with X.
Therefore, the only assumption that is implicit is assumption I.