Sclerenchyma is a strengthening tissue composed of thick-walled dead cells (fibres, sclereids). Evaluate each part:
I. Pericycle in young dicot stems often becomes lignified or sclerenchymatous and contributes to mechanical strength — so it can be sclerenchymatous (Yes).
II. Hypodermis in many monocot stems is formed of sclerenchymatous fibres (Yes).
III. Vascular bundle sheath (the sclerenchymatous bundle sheath) in many monocots is a layer of sclerenchyma surrounding vascular bundles (Yes).
IV. Endodermis in dicot stem is generally a living, parenchymatous layer with Casparian strips (not classically sclerenchyma).
Therefore the sclerenchymatous structures are I, II and III — option (4).