Answer:
C and D on the attached picture.
Step-by-step explanation:
Hello,
At first, it is important to remember that a cyclohexane beat conformation is a possible shape adopted by this molecule.
In this case, boat conformations are said to be in equilibrium, it means a condition at which the opposing force or influence is balanced with the conformation force. In such way, no changes are noticed as a function of time due to their stability. Thus, the two structure attaining the equilibrium are C and D (attached picture) as result of the distancing between the included radicals.
Best regards.