The development team has completed coding and unit testing and has handed over the code for system testing. Your testing team is at the end of the system testing phase. You have decided to perform causal analysis on the defects leaked into the system testing phase from the previous phase and identify improvements. Which of the below defects should be included to give the correct analysis results?

a$.$ User Acceptance testing defects

b$.$ All the system testing defects

c$.$ Unit testing defects

d$.$ Defects rejected by the development team