<p>The correct answer is (B) within.</p>
<p>The phrase "within five business days" means that the delivery will occur before the completion of the fifth business day after the purchase. This indicates a specific time frame and implies that the delivery will be prompt and timely.</p>
<p>The preposition "within" is used to indicate a time frame or limit. In this context, it is used to specify the maximum amount of time it will take for the lighting fixture to be delivered. The phrase "within five business days" suggests that the delivery will occur at some point before the fifth business day following the purchase.</p>
<p>The other options are not suitable in this context:</p>
<p>(A) "Since" is used to indicate a starting point or a specific time in the past. It does not convey the idea of a time frame for delivery.</p>
<p>(C) "Between" is used to indicate a range or interval of time or options. It does not convey the idea of a specific time frame for delivery.</p>
<p>(D) "Above" is used to indicate a higher position or amount. It does not convey the idea of a time frame for delivery.</p>