Statement: Most people who stop smoking gain weight.
Assumptions:
1. If one stops smoking, one will gain weight.
2. If one does not stop smoking, one will not gain weight
Answer: D
The statement talks of most people' and not 'all'. So, I is not necessarily true. Thus, I is not implicit. The condition, if one does not stop smoking, cannot be deduced from the statement. So, II is also not implicit.