Here's why:

* Electron-withdrawing groups increase acidity: Nitro groups (-NO2) are strong electron-withdrawing groups. They pull electron density away from the carboxyl group (-COOH), making the hydrogen more likely to dissociate as a proton (H+). This increases acidity.

* Electron-donating groups decrease acidity: Methoxy groups (-OCH3) are electron-donating groups. They push electron density towards the carboxyl group, making the hydrogen less likely to dissociate. This decreases acidity.

In summary:

* Ortho-nitro benzoic acid: Strong electron-withdrawing group (nitro) enhances acidity.

* Ortho-methoxy benzoic acid: Electron-donating group (methoxy) reduces acidity.

Therefore, ortho-nitro benzoic acid is the more acidic compound.