Let's think about what this statement means in conditional terms:
None of them have heads on both sides
So, if a coin has a head on one side, it does not have a head on the other side:
Head on one side NO Head on the other side
When combined with the other conditional statement in the stimulus, we can prove that answer choice (D) states a contrapositive claim.
Just a reminder: this question - as well as every other question from your Homework - is explained on the Online Student Center.