Longevity pharmacology centres on a handful of nutrient-sensing nodes: mTOR, AMPK, sirtuins, and autophagy. Map each drug to its node.
Rapamycin is the prototypical $mTOR$ inhibitor - correct. Metformin is an $AMPK$ activator that mimics caloric restriction - correct. Resveratrol stimulates $SIRT1$, an $NAD^{+}$-dependent deacetylase - correct.
The odd one out is spermidine. Spermidine is one of the most robust dietary inducers of autophagy; by inhibiting the acetyltransferase EP300 it relieves a brake on autophagy and thereby up-regulates it. The given pairing claims spermidine "decreases autophagy," which reverses its true action. Hence this is the incorrect match.
\[\boxed{\text{Spermidine } \textbf{increases} \text{ autophagy} \Rightarrow \text{option 4 is wrong}}\]