For example, the tense may change between the methods section and the discussion section. The abstract is usually in the past tense due to it showing what has already been studied. Example: “This ...

Most novels are written in the past tense. Readers are more familiar with this tense because they are used to being told a story that has already taken place. For most verbs you add an ‘ed’ at ...

To establish the difference between the use of ‘has/have’ and that of ‘had’, one needs to understand the essence of the past perfect tense.