Final answer:
Sketches are indeed useful when time and circumstances prevent finished drawings, especially in geology, to focus on specific aspects of the subject, as in a fossil sketch.
Step-by-step explanation:
Sketches can indeed be used in place of finished drawings when time and circumstances do not permit the preparation of a finished drawing. This scenario is particularly true in fields such as geology, where sketches are a valuable tool for highlighting and focusing on specific aspects of a subject, like a fossil, in situ. For instance, a sketch of a Triceratops jawbone allows geologists to focus on the important aspects of the fossil by using shading, colors, and annotations to remove distractions such as an unimportant background. This method is effective in emphasizing the relevant details that are crucial for analysis and discussion, which may not always be clear in a photograph. Therefore, the answer to the student's question is true.