The correct answer is: A. None is implicit
The statement is an advertisement for a luxurious flat. It does not say anything about how people can join the upper echelons of society. It also does not say anything about the cost of the flat or how easy it is to book. Therefore, none of the assumptions are implicit in the statement.
Assumption I: It is possible to join the select band of rich people by hard work.
This assumption is not implicit in the statement. The statement only says that people can move into the upper echelons without paying a steep price. It does not say anything about how people can do this.
Assumption II: Staying in luxury without paying steep price is the criterion of upper crust of the society.
This assumption is also not implicit in the statement. The statement only says that people can move into the upper echelons without paying a steep price. It does not say anything about what the criteria for being in the upper echelons are.
Assumption III: Booking a luxurious flat is very easy now.
This assumption is also not implicit in the statement. The statement only says that people can move into the upper echelons without paying a steep price. It does not say anything about how easy it is to book a luxurious flat.