<p>The correct answer is <strong>(D) strictly</strong>.</p>
<p>The word "adhere" means to follow or obey something, in this case, the store's policy. To describe how the GameStop employees follow the policy, we need an adverb that shows that they do it in a precise and exact manner.</p>
<p>(A) "comfortably" does not make sense in this context because it means to do something in a comfortable or relaxed manner, which does not convey the idea of following a policy strictly.</p>
<p>(B) "customarily" means to do something according to custom or tradition. While it is possible that the employees follow the policy customarily, it does not convey the sense of strict adherence that is required in this context.</p>
<p>(C) "dedicatedly" means to do something with dedication or commitment. While it is possible that the employees follow the policy dedicatedly, it does not convey the sense of strict adherence that is required in this context.</p>
<p>(D) "strictly" means to do something in a precise and exact manner, without any deviation. This is the most appropriate adverb to describe how the GameStop employees adhere to the store's policy.</p>
<p>Therefore, the correct answer is (D) strictly.</p>