a.      should only be replaced with similar materials.

b.     should be replaced with asphalt shingles.

c.     could be replaced with wood shingles.

d.     should always be repaired and not replaced.

WRONG

If at all possible, damaged roofing should be replaced with similar materials. If the old roofing was damaged beyond repair, and new framing  was required, asphalt shingles could be used if historic buildings in the same district also used asphalt shingles. But the new roofing should maintain the original pitch (angle) and form (shape).