Refer to the article “From Cave Paintings to Emoji” in your Emoji and Pisa and Birds, Oh My! magazine for a complete version of this text. Where in “From Cave Paintings to Emoji” could a reader find information about the appropriate use of emoji?

a. under the heading “Express Yourself”
b. in the graph on page 17
c. in the timeline entry for 1999
d. under the heading “Smartphones”