a. His perseverance ________ the technique illustrates his single-mindedness and his belief in his own ability. b. The fact that Britain could use air bases and airports in its territory throughout the world was perceived in Washington as an enormous advantage, and contributed to the American insistence ________ free and open competition.c. The colors stand for different things: Guyana’s green land, its mineral resources, the country’s rivers, the energy of the people as they build the nation’s riches and their persistence ________ doing this task.d. His exercise regime is supported by strict adherence ________ a diet, and together they have enabled him to retain a muscular frame with what he claims is zero body fat.