Final answer:
The most secure password is a. Sj49?zT$ due to its combination of uppercase, lowercase, numbers, and special characters.
Step-by-step explanation:
Out of the given options, the password that is most secure is a. Sj49?zT$. It is a strong password because it includes a combination of uppercase and lowercase letters, numbers, and special characters. This makes it harder for someone to guess or crack the password.
The password b. Uber123 is not secure because it is a common word followed by numbers, which can be easily guessed or targeted in a brute force attack.
The password c. Yh30!nP# is secure, but using the same password for all apps on her phone is not recommended. If one app's security is compromised, then all the other apps would also be at risk.
The password d. Vidya#123 is not secure because it includes a common word followed by numbers, which can be easily guessed or targeted.