To answer the question correctly, students must notice both the date of the event and the date of the lithograph, and understand that the gap in time between the two limits the usefulness of the source as evidence of what happened at the Battle of Trenton.
Student explains why the time gap limits the reliability of the source as evidence of what happened at the Battle of Trenton.
Student evaluates reliability of source, but does not fully understand the problems caused by the gap in time.
The student recognizes some aspect of the time gap, but does not fully explain why the gap in time is problematic. For example, the student might mention that the painting is not a "primary" source, but does not explain why this limits the usefulness of the source.
The student discounts the source because a historian would need more than just this one source to determine what happened at the Battle of Trenton. This answer is laudable in that it recognizes the need to corroborate historical sources, but this answer does not directly evaluate the usefulness of this particular source.
The student evaluates the usefulness of the source based on the perspective or biases of the artist. This response shows a sophisticated disposition toward historical sources; historians often consider the perspective of the artist when sourcing a painting. But little is known about the creator of this painting, and an evaluation based on the perspective of the artist would be largely guesswork.
The student evaluates usefulness based on the type of source. For example, a student might reject the source because he or she believes that paintings are not reliable sources of information.
Student does not recognize the gap in time and instead takes the painting at face value or provides an irrelevant response.
The student evaluates the usefulness of the source based on how well it matches his or her historical understanding of the event.
The student evaluates the usefulness of the source based on its aesthetic qualities.