Select all the following statements that are true for operating system (OS) calls. Incorrect selections carry negative marks. Select one or more: 1. Executing a system call in user mode does not always cause a mode switch. 2. A system call is implemented using a trap (or s/w interrupt). 3. Reading from or writing to a file is achieved by an appropriate system call. 4. Executing a system call always causes the process making the call to be rescheduled. 5. The system calls offered by the OS can be thought of as the application programming interface (API) to the OS