An important aspect in the statement of the rules is the distinction between reviewable and nonreviewable plays.

The turmoil went on—no rest, no peace. […] It was nearly eleven o'clock now, and he strolled out again. In the little fair created by the costers' barrows the evening only seemed beginning; and the naphtha flares made one's eyes ache, the men's voices grated harshly, and the girls' faces saddened one.

Now that the length of tangent vector is defined, the magnitude of a differential form is also determined. By making use of this fact we can give a more precise statement to the theorem of de Rham. That is, from the point of view of magnitude, we may prove that within the set of all closed forms representing a de Rham cohomology class, there is one and only one differential form that has the best shape. Such a form is called a harmonic form, and it can be characterized by using a differential operator called the Laplacian.

If you don't know the answer, just stick down any old thing: you might get a mark for it.