Which of the following is an example of ottonian architecture?
a. clerestory
b. gallery
c. arcade
d. all of the above

The answer is "d. all of the above".
Clerestory, gallery and arcade are the examples of Ottonian architecture. 

Ottonian Architecture is a structural style which advanced during the rule of Emperor Otto the Great. The style was found in Germany and endured from the mid tenth century until the mid eleventh century. Ottonian design draws its motivation from Carolingian and Byzantine engineering. Clerestory, gallery and arcade are the examples of Ottonian architecture. In which arcade progression of arches supported by columns, clerestory refers to a clear glass window that is situated close to the top of the church in Ottonian design and gallery is between the arcade and the clerestory.