The correct answer is D) Braided line with a solid core. Braided lines with a solid core are difficult to splice effectively because the solid core does not allow the strands to interweave properly. This makes it challenging to create a strong, reliable splice. In contrast, braided lines with a hollow core and double-braided lines can be spliced, as the hollow core or the two separate layers allow the strands to intermesh and form a secure connection. The other options are incorrect because: A) Braided line with a hollow core can be spliced, and C) Any line can be spliced is not accurate, as braided line with a solid core cannot be effectively spliced.