The correct answer is 2 Key Points Reading the sentence we find that: The error lies in part 2 of the sentence. Here the article 'a' is missing before the word bicycle. The usage on bicycle is wrong and should have an article in front of it. Therefore the part changes to 'school on a bicycle' Thus the correct sentence will be David decided that going to school on a bicycle would be beneficial to him as well as the environment. Additional Information Articles are special modifiers that appear before nouns or noun phrases. Like other adjectives, they help clarify the meaning of the noun in your sentence Here the article helps to modify the noun bicycle.