<s>[INST] context: Exudative RD is characterized by the accumulation of Sub retinal fluid in the absence of retinal breaks or traction. It may occur in a variety of vascular, inflammatory and neoplastic diseases involving the retina, RPE and choroid in which fluid leaks outside the vessels and accumulates under the retina. As long as the RPE is able to compensate by pumping the leaking fluid into the choroidal cir-culation, RD does not occur. However, when the mechanism is overwhelmed or functions subnormally, fluid accumulates in the subretinal space. Sign in exudative RD: The detached retina is very mobile and exhibits the phenomenon of 'shifting fluid' in which SRF detaches the area of retina under which it accumulates . For example, in the upright position the SRF collects under the inferior retina, but on assuming the supine position for several minutes, the inferior retina flattens and SRF shifts posteriorly, detaching the superior retina. Demarcation lines are present in long standing retinal detachmemts. Tobacco dusting is a sign of rhegmatogenous retinal detachmemt. Fixed folds are seen in tractional retinal detachmemt. [/INST] question: Which of the following is most characteristic of exudative retinal detachments? | options: A: Demarcation lines B: Tobacco dusting C: Fixed folds D: Shifting fluid | answer: D </s>