The correct option is B either ; or
Correlative conjunctions are pairs of conjunctions that work together. Some examples are either/or, neither/nor, and not only/but also. The given sentence requires the use of a correlative conjunction. The combination either/or indicates that there is a choice between the two choices, and only one can be selected. Either is always used with or and it is used to express alternatives and or a choice between two (and sometimes more) things. Thus Option B is correct as we have to choose between the premium package or the standard one. The combination neither/nor indicates that neither of the two choices can be selected. In other words, neither choice is available. Thus Option C is incorrect as neither/nor - When they're paired up they negate both parts of a statement. We use' also' in the front position to emphasise what follows or to add a new point or topic and 'not' is used to indicate negation. Both cannot be used together. Thus Option A is incorrect. While the given sentence refers to an alternative between the premium and the standard for the speaker to choose, the usage of 'not but' indicates' to exclude and include'.Thus Option D is incorrect.