The correct answer is: B. Manages the use of extended memory.
HIMEM.SYS is a device driver that allows DOS to access extended memory. Extended memory is memory above 1MB that is not available to DOS by default. HIMEM.SYS manages the use of extended memory by providing a virtual memory manager that allows DOS to use extended memory for programs and data.
A. Supports (ANSI) terminal emulation is incorrect because ANSI.SYS is the device driver that supports ANSI terminal emulation.
C. Uses expanded memory on a 80386 processor is incorrect because EMM386.EXE is the device driver that uses expanded memory on a 80386 processor.
D. Supports code page switching is incorrect because CODEPAGE.SYS is the device driver that supports code page switching.
E. None of the above is incorrect because HIMEM.SYS does manage the use of extended memory.