The first two and a half years of American control of the Panama Canal were devoted only to preparation for human living. Energies were committed to establish suitable houses, hotels, and kitchens. Food supplies were built up and the ability of the existing Panama Railway system was increased. In addition, a large Panama Canal labor（港口） force was enrolled (招收) and organized under a civil government. With all this activity, the need for improved sanitation(卫生) soon became obvious . Improving the unclean conditions was one of the greatest difficulties in building the Panama Canal. Colonel William C. Gorgas stepped up and took charge of improving these sanitary(卫生的) and working conditions.
With the leadership of Gorgas, many new departments of sanitation were founded. Separate departments each undertook different tasks. Some health departments were in charge of hospitals, others in the management of health matters, and still others took charge of sanitation inspections. Committees were also formed to look after the basic welfare of the laborers.
The sanitation work included clearing land, establishing quarantine(检疫) facilities, and taking care of sick and injured laborers in hospitals. On top of this, an operation under Gorgas' command aimed to destroy the yellow fever and malaria（疟疾）- carrying mosquitoes（蚊子）。
The big wetlands surrounding the canal in certain areas were a great breeding(繁殖) ground for mosquitoes. In an attempt to solve some of the mosquito problems, the surrounding wetlands were drained(排干水) and filled. Various methods were used. This task was so big that the first two years of building the canal were largely dedicated to getting rid of the mosquitoes. In the end, these efforts were a success. By 1906, yellow fever was virtually wiped out in canal areas and the number of deaths caused by the other top disease, malaria, was also reduced significantly.
With all these new health measures, the canal area has become one of the healthiest regions in the world. With the leadership of Gorgas, the department of sanitation helped to make the canal construction possible.
39. This passage is mainly about ________.
A. the health measures during the construction of the Panama Canal
B. the leadership of Gorgas in the construction of the Panama Canal
C. the first two years of American control in the Panama Canal
D. the process of the construction of the Panama Canal
40. Led by Gorgas, many departments were set up to do various tasks except _______.
A. inspect sanitation B. watch over health matters
C. take charge of hospitals D. enroll labour force
41. What Colonel William C. Gorgas thought most important was to _______.
A. remove the grasses and bushes B. establish quarantine equipment
C. destroy mosquitoes D. attend to sick laborers in hospitals
42. The author tells the readers that _______.
A. yellow fever and malaria are caused by waters and wetlands
B. the wiping out of yellow fever reduced the number of malaria deaths
C. the climate in the canal areas was suitable for mosquitoes to grow
D. the two-year sanitation work stopped the outbreak of yellow fever