Question

Central cell of the embryo sac contains:
A. A single haploid nucleus.
B. Two haploid polar nuclei.
C. One diploid fusion or secondary nucleus.
D. Either [b] or [c]

Answer 1

Hint: In angiosperms, the gametophyte is known as the embryo sac. It is very small and has only a few nuclei, usually eight; the cytoplasm is not divided by the cell walls and is more or less directly linked to these nuclei.


Step by step solution:
The female gametophyte of angiosperms, known as the embryo sac, has eight nuclei in total, including the egg, two central nuclei that will combine with one of the pollen nuclei to form the endosperm, three antipodal nuclei at the end of the embryo sac across from the micropyle, and two short-lived synergids that are close to the micropyle. These nuclei disintegrate quickly after fertilisation, just as synergids. Each synergid has two nuclei, and an egg cell also has one nucleus. There are two synergids in total. It coexists with synergid in the micropyle. The micropyle contains three nuclei in total. The central cell, which has two polar nuclei, is at the centre. Three antipodals are found at the Chalazal end, with a total of three nuclei in all between each antipodal. Cytoplasmic polarity in the egg is the reverse of synergids'.These are the embryo sacs' vegetative cells also called antipodals. The central cell, which makes up the majority of the embryo sac, originally has two polar nuclei and shortly before fertilisation develops a secondary nucleus or definitive nucleus (2n).


So, option D is correct.

Note: This form of embryo sac has an egg apparatus with 2 synergids and 1 egg cell, 3 antipodal cells at the chalazal end, and 1 central cell, it should be highlighted. Seven cells total from all of these.
Except for the centre cell, each of these cells has one nucleus. Only the central cell has two polar nuclei, thus there are a total of eight nuclei in total.