Answer:
See explanation
Step-by-step explanation:
In the attached picture you have the newman projections of the CHI2CH2I conformations.
We can see that we have 6 conformations there.
Now, which one is the most stable?. This will be the conformation where the Iodine groups are in opposite directions. That's because, for any kind of reaction that this conformation has, it will be easier for the nucleophyle or electrophyle to do a reaction, with the less steric hindrance of atoms, and also the speed and rate of reaction is better.
In this case, the most stable structure (Depending of the point of view of course) will be either C. We hava Carbon 1 in the upward direction, and carbon 2 downward. In these positions both of the iodine are in opposite directions, so, there's less teric hindrance and acid base reactions could be done easily.
According to the above, the least stable conformer will be the eclipsed one with the Iodine, cause they are bigger atoms than the Hydrogen atoms, and therefore, there will be more steric hindrance, and reaction will be slower or it'll give different products. In this case, the most eclipsed conformer is either F or B.