If You Saw a Graph with Rectangles Standing on a Horizontal

If you saw a graph with rectangles standing on a horizontal axis, what is the best immediate visual clue to determine whether it is likely to be a well-designed bar chart or a histogram?

A) If the x-axis has numbers or labels.
B) If the y-axis goes to zero or some other number.
C) Whether it is black and white or in color.
D) Whether the bars are solid or filled with patterns.