Right answer: Church
The Expiatory Temple of the Sagrada Familia (called by all in a simplified way as Sagrada Familia) is a Catholic basilica designed by the famous architect Antoni Gaudí.
This majestic church, considered Gaudí's masterpiece and the greatest exponent of Catalan modernist architecture, was started in 1882 and after the death of Gaudí in 1926 several generations of architects have been commissioned to continue the work that has not yet been completed.
The Sagrada Familia is the most known and characteristic monument of Barcelona and despite being an unfinished work, thousands of tourists go every day to contemplate it.
Thererfore the correct option is C, and the whole sentence is:
In Barcelona, you should plan to see the famous Church of the Sagrada Familia
