Final answer:
The first planned hybrids of plants were developed before the 18th century by early agriculturalists who selected for favorable traits, making the statement (b) False.
Step-by-step explanation:
The first planned hybrids of plants were actually developed earlier than the 18th century. This topic falls under the history of agriculture and the advancement of agricultural practices. Early genetic engineers, or 'primitive' agriculturalists, selected for plants that had favorable traits thousands of years ago. These included hybridization practices that saw the combination of different strains of plants to produce desirable characteristics. A key figure in understanding this further is Gregor Mendel, who in the 19th century, crossed plants that were true-breeding for certain flower colors to observe inheritance patterns, leading to the creation of hybrid plants. Therefore, the correct answer is (b) False, as plant hybridization took place before the 18th century.