What problem can occur from using too much pressure in a sketch?

Correct answer: The lines will become difficult to erase

The governing concept is controlled line quality in pencil sketching. Excessive pressure produces very dark marks and may indent or bruise the paper, so the lines cannot be erased cleanly. It also uses more graphite, not less. Heavy pressure alone does not create convincing depth; depth depends on accurate form, light direction, and gradual tonal changes. Therefore option C describes the actual problem.