<p>As of January 1, 2021, Singapore Air will <strong>(A) charge</strong> a no-show penalty to Singapore Air ticket holders who cancel boarding after entering the departure area.</p>
<p>The correct answer is <strong>(A) charge</strong>.</p>
<p>The verb "charge" is the most appropriate choice in this context. In this sentence, "charge" means to impose a fee or penalty on someone. The phrase "no-show penalty" indicates that there will be a financial consequence for passengers who cancel their boarding after entering the departure area. Therefore, the airline will charge a fee to these passengers as a penalty for their cancellation.</p>
<p>The other options do not fit the context:</p>
<p>(B) "Enroll" means to officially register or join a program or organization. It does not make sense in the context of imposing a penalty for cancelling boarding.</p>
<p>(C) "Restrict" means to limit or control something. While the airline may have restrictions on cancellations, it does not fit the context of imposing a penalty.</p>
<p>(D) "Verify" means to confirm or check the accuracy or truth of something. It does not fit the context of imposing a penalty for cancellations.</p>