A. SQLmap would be the best automated tool to use next to try to identify a vulnerability in this URL, specifically an SQL injection vulnerability. SQLmap is an open-source tool that automates the process of detecting and exploiting SQL injection vulnerabilities. It can take a URL as input, such as the one provided in the question, and automatically test for SQL injection by injecting different payloads into the parameters of the URL, such as the "id" parameter in this case.
B. Nessus is a vulnerability scanner that can identify vulnerabilities in a wide range of systems and applications, but it is not specific to web application vulnerabilities.
C. Nikto is a web server scanner that can identify a wide range of vulnerabilities in web servers and web applications, it's also useful to identify misconfigurations, but it's not specific to SQL injection vulnerabilities.
D. DirBuster is a tool that can be used to identify directories and files on web servers, it's not specific to web application vulnerabilities.