Which part of the following sentence contains an error? There is no doubt (a) that hard work (b) paves the way (c) to success. (d)

The idiomatic expression in English is 'pave the way FOR (something)', not 'pave the way TO (something)'. The correct sentence should read: 'There is no doubt that hard work paves the way FOR success.' The error is in part (d) where the preposition 'to' is used instead of 'for'. Parts (a), (b), and (c) are grammatically correct.