47. John is_____ most hard-working student I’ve ever known. A. the B. Ø C. a D. an 48. The Titanic sank while it was crossing _____Atlantic ocean. A. a B. the C. an D. Ø (no article) 49. I went to _______ libreary to borrow some books. A. a B. an C. the D. X 50. My brother can play _______ piano beatifully. A. a B. an C. the D. no article 51. _______ sun gives us heat and light. A. A B. An C. The D. X 52. Peter didn’t go to school yesterday because he had _______ toothache. A. a B. an C. the D. no article 53. Laura’s brother is _______ engineer. A. a B. an C. the D. no article