Q.Identify X, Y and Z in the given figure :

In a mature 7-celled, 8-nucleate embryo sac, the micropylar end carries the egg apparatus (2 synergids + 1 egg), the centre has the diploid definitive (secondary) nucleus, and the chalazal end has 3 antipodal cells. So X = synergid (n), Y = definitive nucleus (2n), Z = antipodal cell (n).

Note: this item carries a figure. A specific figure description was not supplied to me in the batch, so I answer from the standard NCERT embryo-sac diagram and internal consistency of the options.

Structure of the mature female gametophyte (embryo sac):

• Micropylar end — the egg apparatus: two synergids (n) flanking one egg cell/ovum (n).
• Centre — the large central cell with two polar nuclei that fuse to form the definitive (secondary) nucleus (2n).
• Chalazal end — three antipodal cells (n). …