15. Which graph represents an exponential equation?

The answer is D because  The graph passes through the point (0,1) and the graph is increasing.

i hope this helps

in geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel. by extension, a line and a plane, or two planes, in three-dimensional euclidean space that do not share a point are said to be parallel.