The correct answer is: C. Either I or II is implicit.
The statement “Please do not use lift while going down” does not provide enough information to determine whether assumption I or assumption II is implicit. It is possible that the lift is unable to carry any load while going down, but it is also possible that the lift is available for use while going down, but the management has asked people not to use it in order to conserve energy or for some other reason. Similarly, it is possible that the provision of lift is a matter of facility and not of right, but it is also possible that the provision of lift is a matter of right, but the management has asked people not to use it in order to prevent accidents or for some other reason. Therefore, either assumption I or assumption II could be implicit in the statement, but it is impossible to say for sure without more information.