Answer:
D) both groups are equatorial.
Explanation:
To solve this question we can start by drawing the molecule in using the <u>structure of the hexagon</u>. In this structure, we have the methyl group on carbon 1 and the terbutyl group on carbon 3, additionally, if we have a cis structure both groups must have the same type of bond (in this case the wedge bond). (See figure 1)
When we write the <u>chair structure</u>, we must keep the same structure. That is, methyl must be on carbon 1 and terbutyl on carbon 3. Also, the cis configuration must be maintained. With this in mind, we can choose the <u>equatorial configuration</u> for methyl on carbon 1 (since the position equatorial is the one that has <u>less steric impediment and more stability</u>). If this is true for carbon 1, we must place the terbutyl group on carbon 3 in the same configuration (i.e. cis). Therefore, on carbon 3 we must place the tert-butyl down on carbon 3, that is, in the <u>equatorial position</u>. (See figure 1).
Therefore, in the chair-like structure, both groups must be in an equatorial position.
I hope it helps!