Research indicates that facial expression and tone of voice account for _______ percent of communication between two people.

Artists often use graphite pencils for drawing __________

A. when they run out of pen and ink B. if they are working in the outdoors C. because they have lead in them D. because they can get different effects due to the many grades of hardness of the medium

A hemispherical vault built atop a circular or polygonal base is called __________.

a. a pendentive b. an arcade c. a dome d. a buttress