Which of the following is considered a strong password?

A strong password is one that is difficult for others to guess and provides a higher level of security against unauthorized access. The choice identified as a strong password includes a mix of upper and lower case letters, numbers, and special characters, making it more complex and thus harder to crack. This complexity is key in safeguarding accounts against various attack methods, including brute-force attacks.

In contrast, the other options lack this level of strength. For instance, "123456" is overly simplistic and commonly used, making it easy for attackers to guess. "Fido," while easy to remember, is too short and does not incorporate any numbers or special characters, which weakens its security. "June1970" uses a recognizable word and a common date, which decreases its effectiveness as a password since it could be easily guessed based on personal information.

The choice of Sch24@sg? represents a well-constructed password that adheres to best practices for creating secure passwords, making it the most effective option for protecting sensitive information.