Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the best option for each of the blanks.
The Eighth Wonder of the World The Thames Barrier is a major part of the flood defense scheme for protecting London (35) ______ rising water levels. The defenses (36) ______ include raised river embankments and additional flood gates at strategic points, including the Barking Barrier. The unique structure that is the Barrier spans the 520- metre wide Woolwich reach and (37) ______ of 10 separate movable gates, each pivoting and supported between concrete structures which house the operating machinery. When raised, the four main gates (38) ______ stands as high as a five-storey building and as wide as the opening of Tower Bridge. Each (39) ______ 3700 tones. During the first twelve years of operation the Barrier has been closed twenty nine times to protect London.