The difference between a vulnerability assessment and a penetration test is that a vulnerability assessment: 
A、searches and checks the infrastructure to detect vulnerabilities, whereas penetration testing intends to exploit the vulnerabilities to probe the damage that could result from the vulnerabilities. 
B、and penetration tests are different names for the same activity. 
C、is executed by automated tools, whereas penetration testing is a totally manual process. 
D、is executed by commercial tools, whereas penetration testing is executed by public processes.