Q.Pick out the odd pair.

Step 1. Check pair (a): mass selection is indeed based on grouping plants by morphological/phenotypic characters — correctly paired.

Step 2. Check pair (b): pureline selection is indeed produced by repeated self-pollination of a single homozygous individual — correctly paired.

Step 3. Check pair (c): the chapter defines clonal selection as applying to asexually propagated crops, where mitotically derived progeny match the parent genotype — pairing it with 'sexually propagated' is therefore wrong.

Step 4. Check pair (d): natural selection is indeed the process operating in nature — correctly paired.

Check each pair against the chapter's own definitions of the three artificial-selection types plus natural selection.

• Assuming clonal propagation involves sexual reproduction because it still produces new plants.
• Overlooking that mass selection is correctly defined by morphological similarity in option (a), and mistakenly flagging it instead.