The correct tag question for a statement with "haven't got" is "have we?". However, among the given options, "haven't we?" is the most appropriate choice to maintain the negative-positive structure of tag questions when the main verb is "have got".
The sentence is "We haven't got much time".
The auxiliary verb is "have" (from "haven't got").
The subject is "we".
Therefore, the tag question should be "haven't we?" to match the negative statement.