Let's analyze both molecules step by step: ### Left Molecule: Most Acidic Hydrogen This molecule is cyclopentadiene (a five-membered ring with two double bonds and hydrogens). The most **acidic hydrogen** is the one whose removal leads to the most stable conjugate base. In cyclopentadiene, if you remove the hydrogen from the **carbon between the two double bonds** (the one that is sp³ hybridized, not part of the double bonds), the resulting anion is resonance stabilized and aromatic (6 π electrons, Hückel’s rule). This hydrogen is much more acidic than the others because of the stability of the aromatic cyclopentadienyl anion. So, **the most acidic hydrogen is the one on the sp³ hybridized carbon (the only CH₂ group in the ring, between the two double bonds).** Highlight this hydrogen. ### Right Molecule: Most Basic Site This molecule is pyridine (a six-membered aromatic ring with one nitrogen atom). The **most basic site** in pyridine is the **nitrogen atom** itself. The lone pair on the nitrogen is not involved in the aromatic π system and is available to accept a proton, making it the most basic site. So, **highlight the nitrogen atom in the ring** as the most basic site. ### Final Answers - For the left molecule (cyclopentadiene), highlight the hydrogen on the sp³ carbon between the two double bonds. - For the right molecule (pyridine), highlight the nitrogen atom in the ring. These are the most acidic hydrogen and the most basic site, respectively, with explanations based on resonance stabilization and basicity of lone pairs.