Final answer:
The correct answer to the student's question is 'adhesive.' Lacing and couching are conservation framing techniques that use threads to secure artwork without harmful adhesives.
Step-by-step explanation:
Lacing and couching are techniques used in conservation framing to mount artwork without causing damage. These methods do not use any adhesive or tapes, which can be harmful to art over time. Instead, they use a network of threads or stitches to hold the artwork in place. Therefore, the correct answer to the question is 'd) Adhesive'.