完形填空
阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。
Healthy Food
Street sellers, particularly in developing countries, supply large amounts of food __1__ people on low incomes. This sector also employs some 6-25% of the work force, mainly women, in developing countries, and provides markets for agricultural and other produce. In many countries, __2__, the authorities are not willing to recognize it __3__ a formal sector of the food supply system, they may ignore it in food control programs or even try to put an end to ___4___.
There are two possible contaminants: pathogenic micro-organisms ___5___ hazardous chemicals. As ___6___ as micro-organisms are concerned, there is apparently no convincing evidence that street foods are more involved in the transmission of infection than foods obtained in, e.g. hotels. Studies in Egypt and elsewhere have found street foods to compare not unfavorably with hotel ___7___ in respect of contamination with micro-organisms—some street foods were found to be contaminated with pathogens, but so were foods from four-and five-star ___8___ in the same area.
Hazardous chemicals have been found in street foods, and food exposed for sale on roadsides may become contaminated by lead from vehicle exhausts. Health dangers may arise ___9___: purchase of raw ___10___ of poor quality; improper storage, processing, and cooking, leading ___11___ reuse of water; limited piped drinking-water; lack of refrigeration; unsatisfactory waste-disposal facilities; and personal cleanliness.
The authorities should take ___12___ account the potentials of different categories of food for transmitting disease, and should control appropriately for the different __13___—sellers of bottled drinks require less control than those of food. Dry foodstuff, dried grains, and sugared foods are less likely to transmit disease than gravies, cooked rice, and low-acid milk, egg, and meat products. Similarly foods which are thoroughly cooked and eaten at ___14___ are safer than precooked food kept at high temperatures ___15___ several hours.
1. A for B on C by D at
2. A but B however C besides D what
3. A to B about C as D of
4. A them B those C its D it
5. A and B or C for D with
6. A farther B far C more D many
7. A disease B diseases C food D foods
8. A hotels B houses C buildings D generals
9. A at B with C from D to
10. A food B thing C matters D materials
11. A to B about C from D around
12. A at B to C into D in
13. A price B prices C category D categories
14. A once B twice C all D home
15. A about B at C before D for
