Which of the following is the best advice?2 points towards your certificateGive users feedback on their passwords only once they have submitted them for analysis.It can be a problem to enable users to retrieve their passwords through the system.Only let users successfully register passwords that feature symbols, but no numbers with letters.

The best advice among the options given is "Only let users successfully register passwords that feature symbols, but no numbers with letters." This is because it encourages the creation of strong, complex passwords. Strong passwords often include a mix of letters, numbers, and symbols, which can be more difficult for others to guess or for hacking tools to crack.

However, it's important to note that this advice could be improved. The strongest passwords are not only composed of symbols, but also a mix of uppercase and lowercase letters, numbers, and symbols. Additionally, they should be long (at least 12 characters is often recommended) and not easily guessable (i.e., they shouldn't include obvious personal information or common words/phrases).

The other two options are not as advisable:

1. "Give users feedback on their passwords only once they have submitted them for analysis." This could potentially be a security risk, as it might involve sending the password over the internet, where it could be intercepted. It's better to give users feedback as they're creating their password, without the password leaving their local device.

2. "It can be a problem to enable users to retrieve their passwords through the system." While it's true that password retrieval systems can sometimes be exploited by attackers, they're also necessary for user convenience. If a user forgets their password and there's no way to retrieve it, they could be locked out of their account. The key is to design password retrieval systems that are secure, such as by using two-factor authentication.