Option D is correct because linear tender swelling along the internal jugular vein is a more specific sign of thrombophlebitis, while lymphadenitis tends to be isolated oval swelling in anatomical lymph node locations. | Option A is incorrect as high fever is present in both conditions; Option B is incorrect as elevated WBC is non-specific and occurs in infections generally; Option C is incorrect as neck pain is present in both conditions; Option E is incorrect as pharyngeal congestion is part of primary infection in both conditions. | Contrast-enhanced CT is requested immediately when linear cord-like tender swelling is palpated along jugular vein to confirm venous thrombosis. | Presence of multiple mobile bilateral lymph nodes instead of unilateral linear swelling changes the answer to indicate viral or simple bacterial lymphadenitis. | In consultant practice, palpable "jugular cord sign" is nearly pathognomonic for Lemierre syndrome. | Sources: Scott Browns Otorhinolaryngology 8th edition volume 1.pdf — pp. 503, 505; Controversies in Otolaryngology.pdf — pp. 124, 125.