The term ‘clone’ cannot be applied to offspring formed by sexual reproduction because

Answer: (a) offspring do not possess exact copies of parental DNA

A clone is an individual that is morphologically and genetically identical to its parent. In sexual reproduction, the offspring gets half its DNA from each of two parents, and crossing over and independent assortment during meiosis shuffle the genes further. So the offspring is not an exact copy of either parent's DNA and cannot be called a clone.

Option (b) describes asexual reproduction, (c) is irrelevant, and (d) is wrong because offspring share half their DNA with each parent.