In dicot stem, xylem is
A.Polyarch – stele with many xylem strands, is found in monocot roots.
B.Monoarch – stele with one xylem strand, is found in Trapa.
C.Endarch – protoxylem is present towards the centre, and metaxylem is present towards the periphery, is found in dicot and monocot stems.
D.Exarch – protoxylem is towards the periphery, metaxylem is towards the centre, is found in dicot and monocot roots.
So, the correct option is ‘Endarch’.