How can Alejandro make a payment if he forgot his wallet but has his smartphone?

Using a mobile payment app on his smartphone is an effective way for Alejandro to make a payment if he forgot his wallet. Mobile payment apps allow users to link their bank accounts, credit cards, or debit cards and process transactions directly through their phones. This method is not only convenient but also secure, as it often includes features like fingerprint verification or facial recognition to authenticate payments.

In contrast, writing a paper check, asking for a loan, or borrowing cash from a stranger are less practical or safe solutions. Writing a check requires physical access to the checkbook, which is not available without the wallet. Taking out a loan involves additional steps and may not provide immediate access to cash. Additionally, borrowing cash from a stranger poses security concerns and is not advisable as it can lead to potentially unsafe situations.