Which of the following statements are true?

A. Though threads within a process share the same address space of the parent process, we still need to perform context switch for thread switch.

B. Once the context switch is done properly, there is no need to worry about the interference among threads

C. A user-level thread library is designed to not perform context swiches upon thread switches. but requires the user programs to save registers when needed. This thread library is valid and may improve performance.

Give your answer by listing the leading indexes of the true statements in alphabetical order without any separators or spaces (e.g., ABD).