Final answer:
The book of Acts includes the key idea of 'Church' which focuses on the establishment, spread, and role of early Christian communities as the faith grew from Jerusalem to Rome. The correct answer is option c).
Step-by-step explanation:
One of the five key ideas in the book of Acts is Church. The book of Acts details the establishment and spread of the early Christian Church following the death and resurrection of Jesus Christ. It emphasizes the role of the Holy Spirit in guiding the apostles, the importance of forming Christian communities (Church), and discusses the growth of Christianity from Jerusalem to Rome. The early Christian Church was remarkable for its universalism and lack of social distinctions, which diverged from the rigid social hierarchy of the Roman Empire. Additionally, Acts reflects on the challenges faced by Christians and their perseverance in spreading the Gospel through missionary work, leading to the establishment of the church as a key institution in Christianity.