Final answer:
The false statement is that molecules must have a double bond to be cis-trans isomers, while the use of synthesis to confirm the structure and stereochemistry of a natural product is true.
Step-by-step explanation:
The statement that is false among the given options is:
b. Molecules must have a double bond to be cis-trans isomers.
Regarding the question about the confirmation of the structure and stereochemistry of a natural product, the statement that synthesizing the proposed structure and then comparing its properties is a common method for confirmation is true. With respect to the SEO keywords 'structural isomers', 'stereochemistry', and 'natural product', structural isomers are indeed molecules with the same molecular formula but different bonding sequences, while stereochemistry involves the study of the three-dimensional arrangements of atoms within molecules, and a natural product refers to compounds found in nature that often have complex structures.