<p><span style="font-size: 13.008px;">The correct answer is (D) </span><i style="font-size: 13.008px;">complicated</i><span style="font-size: 13.008px;">.</span><br></p>
<p>In this sentence, the word "complicated" is used as an adjective to describe the mobile devices. The adjective form of the word is needed to match with the subject "devices" which is plural. The word "unnecessarily" indicates that the devices are more complicated than they need to be.</p>
<p>Here's how each option would fit in the sentence:</p>
<p>(A) complication - This is a noun form and does not match with the subject "devices".</p>
<p>(B) complicates - This is a verb form and does not match with the subject "devices".</p>
<p>(C) complicate - This is a verb form and does not match with the subject "devices".</p>
<p>(D) complicated - This is the correct adjective form of the word that matches with the subject "devices".</p>