What is the subject of the personifications on the lower eight panels on Andrea Pisano's bronze doors for the baptistery of San Giovanni?

The intersection at right angles of two tunnel vaults is a called:

a. an angular vault. b. a pendentive. c. a groin vault. d. all of these. e. none of these.

The __________ as a technological and agricultural device did not come into use until the twelfth century

A) serf B) catapult C) horse D) plow E) slave