The most stable confomation of cis-1,4-di-t-buty1 cyclohexane is:

Explanation

Remark: An axial t-butyl group is very unfavourable form. In Cis-1,4-dit-dit-t-butyl cyclohexane, one t-butyl group would be forced axial if the compound existed in a chair conformation, to avoid this, the compound prefers to pucker into twist boat so that the two groups can both be in equatorial position (or Pseudoequatorial, since this is not a chair).