Which two letters are often mistaken for numbers due to their similar appearance?

The correct answer is based on the common visual similarity between the letters O and the number 0. In many fonts, particularly sans-serif fonts, the letter O and the number 0 can appear nearly identical, making it easy to confuse them in certain contexts, such as in passwords, codes, or other text that may mix letters and numbers. This similarity can cause issues in readability and comprehension, especially in situations where accuracy is crucial.

In contrast, while I and L also share some visual similarities with numbers in certain contexts, especially in particular typefaces, they are generally less likely to be confused than O and 0. The letters A and 4 have differences in their structure that make them less prone to mix-ups. Similarly, O and Q, while they do look related, have distinct features that usually set them apart visually. Hence, O and 0 remain the most commonly confused characters due to their nearly identical shapes across various fonts.