The answer is C. This is because but is being used as a conjunction separating independent clauses in the other answers. You can remove but from A, B, and D, and you are left with 2 simple sentences.
I hope this helps!!!
1. Cope, treat, control, handle, treat
2. trouble, worry, dilemma
3. Relax, unwind, rest, unlax
4. Healthy, healthful
5. Adequate, abundant, decent, sufficing
6. Daily, day-to-day, often, periodically, regularly, regular, routinely
7. belittle, criticize, slam, slander,
8. abounding, bounteous, bountiful, countless, innumerable, plentiful
9. Cramped, inflexible, solid, rigid, stiff, tense, tightened
10. Depressed, morose, pessimistic, unhappy, blue, destroyed, dispirited, down, dragged low, bad, cast-down, glum, grim, let-down, low-spirited, woebegone
11. Afraid, anxious, panicky, startled, petrified, shaken, terrified, aghast, panic-stricken, terror-stricken
12. Fatigue, weariness, debilitation, enervation, expenditure, feebleness, lassitude, prostration
