Vascular bundles in monocotyledons are considered closed because :
Cambium is absent
there are no vessels with perforations
Xylem is surrounded all around by phloem
A bundle sheath surrounds each bundle
Tunica corpus theory was proposed by
Complex tissue includes
Interfascicular cambium develops from the cells of
In dicot stem, secondary xylem lie towards the ...$A$... and secondary phloem lie towards the ...$B$...
Choose the correct combination of options for $A$ and $B$