Which statement about the trap instruction is NOT true?

Select one:

a. A user program can use trap to request the operating system to do something

b. trap can be used to request input/output

c. trap can be used to request that the program should be terminated

d. Whenever trap is executed, it always halts the program

e. When a trap is executed, the three register parameters contain

codes telling the operating system what the user wants to do