The correct answer is option 3: anticline.

An up fold in rock refers to a geological structure where rock layers are bent or folded upwards in a convex shape. This type of fold is known as an anticline. It is characterized by the oldest rock layers being located at the core or center of the fold, while the newer rock layers are found on the outer edges. The upward folding of the rock layers in an anticline is usually a result of compressional forces within the Earth`s crust, such as tectonic plate movements.

Let`s examine the other options for better understanding:

- Option 1: Graben - This term refers to a type of down-faulted block of land, where the central block sinks between two parallel faults. This is not an up fold in rock, so it is not the correct answer.

- Option 2: Horse - In geology, a horse refers to an isolated block of rock that has been thrust or pushed upwards due to tectonic forces. This is not specifically an up fold in rock, so it is not the correct answer.

- Option 4: Syncline - A syncline is a type of fold in rock where the rock layers are bent downwards in a concave shape. This is the