Final answer:
The given statement that a picture frame is rectangular is an appropriate definition, accurately describing the typical shape of a picture frame with four sides and right angles.
Step-by-step explanation:
The question "The picture frame is rectangular" is asking for a determination of whether the given definition is adequate. To answer this, option (d) 'definition is appropriate' would be correct if we assume that the term rectangular refers to a shape with four sides where opposite sides are parallel and all angles are right angles. The width and height of the frame are not equal, with one dimension being longer than the other. For example, if the width is larger than the height, the frame is considered to be in landscape orientation. This is indeed the correct definition of a rectangular shape, and such a description would apply to most picture frames. Therefore, the definition given ('The picture frame is rectangular') is not too broad, too narrow, or otherwise inappropriate; it accurately describes the shape of a typical picture frame.