Questions

Except pineapple remaining all three are types of apples.

Pineapple is what kind of apple isn't an apple.

When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.

Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

Answer A is incorrect because the WBS hierarchy does not prevent duplication by itself. Answer C is incorrect because a WBS is focused on deliverables and components or work packages and not on tasks. Answer D is incorrect because a WBS can be sized appropriately to the project size with as many levels as necessary.