InEucalyptus(a) Pollen grains and ovules are developed in specialised structures called cones(b) Ovules are naked(c) Female sex organ consists of an ovary, style and stigma(d) All megaspores within an ovule divide to form embryo sac

The statement provided seems to be a mix of different statements about the Eucalyptus plant and its reproductive system. Let's break it down:

(a) In Eucalyptus, pollen grains and ovules are not developed in specialized structures called cones. This is a characteristic of gymnosperms, not Eucalyptus which is an angiosperm. In Eucalyptus, pollen is produced in the anthers (male reproductive organ), and ovules are produced in the ovary (female reproductive organ).

(b) The ovules in Eucalyptus are not naked. This is again a characteristic of gymnosperms. In Eucalyptus, the ovules are enclosed within an ovary.

(c) The female sex organ in Eucalyptus does consist of an ovary, style, and stigma. This is a characteristic of angiosperms. The ovary contains the ovules, the style is the structure that supports the stigma, and the stigma is where pollen is received.

(d) In Eucalyptus, not all megaspores within an ovule divide to form the embryo sac. Typically, one megaspore undergoes mitosis to form the embryo sac, which is the female gametophyte. The other megaspores usually degenerate.