This question evaluates the understanding of passive voice structure in English. **Core Concept:** Passive voice is formed using a form of 'be' + past participle, and it emphasizes the action rather than the doer of the action. **Correct Answer (B):** 'The report was written by the team' correctly uses 'was' (a form of 'be') and 'written' (past participle) to form the passive voice. The focus is on the report being written, with the 'team' mentioned as the doer using 'by.' **Incorrect Option Analysis:** * **A:** 'The cat chased the mouse' is in the active voice, where the cat (subject) does the chasing (action) of the mouse (object). * **C:** 'She is reading a book' is in the active voice, focusing on she who is doing the reading. * **D:** 'They will build a house' is in the active voice, focusing on they who are doing the building. **Key Points:** The passive voice highlights the action, with the doer of the action often being less important or unknown. **Error Prone Areas:** Students may mistake active voice sentences for passive voice or incorrectly form the passive structure. Recognizing the 'be + past participle' pattern is key.