<p>The correct answer is (A) affiliation.</p>
<p>The word "affiliation" is the most suitable choice to complete the sentence. In this context, an affiliation refers to a formal relationship or partnership between two entities, in this case, the company and the courier company. This affiliation is believed to be beneficial to both parties, suggesting that they will work together closely and cooperate to achieve mutual benefits.</p>
<p>Option (B) "retention" is incorrect because it refers to the act of keeping or retaining something, such as customers or employees, and does not fit the context of a partnership between two companies.</p>
<p>Option (C) "support" is incorrect because while support can be provided in a business relationship, it does not convey the idea of a formal partnership or affiliation.</p>
<p>Option (D) "assistance" is incorrect because it implies one party providing help or aid to another, rather than a formal partnership or affiliation.</p>