The reference point in motion is:
A. the point in space and time at which the motion ended.
B. the focal point.
C. the point in space and time at which the motion began.
D. the origin.

With the largest atoms and the smallest number of valence electrons and with the smallest atoms and the greatest number of valence electrons are the most reactive. a. nonmetals; metals b. nonmetals; transition elements c. transition elements; metals d. metals; nonmetals