Final answer:
The church built in 1848 at The Rocks, Sydney is called the Garrison Church, a historical military church.
Step-by-step explanation:
Built in 1848, the name of the church at The Rocks, Sydney is C) Garrison Church. The Garrison Church, officially known as the Church of Holy Trinity, was the first military church built in colonial Australia and serves as an important historical landmark. It was built to cater to the spiritual needs of the British soldiers stationed in Sydney at the time, hence the name 'Garrison' Church.