第6部分：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，涂在答题卡相应的位置上。
Healthy Food
Street sellers, particularly in developing countries, supply large amounts of food _____(1) people on low incomes. This sector (部门) 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 as a formal sector of the food _____(3) system; they may ignore it in food control programs or even try to put an end to _____(4).
There are two possible contaminants (污染物): pathogenic (病原) micro-organisms (微生物) _____(5) harmful 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 (病原菌), but so were foods from four, and five-star _____(8) in the same area.
Harmful chemicals have been found in street foods, and food exposed for sale on roadsides, may become _____(9) by lead from vehicle exhausts.
Health dangers may arise from: purchase of raw materials of _____(10) quality; improper storage, processing, and cooking, leading _____(11) reuse of water; limited piped drinking-water; lack of refrigeration (冷藏); unsatisfactory waste-disposal facilities; and personal cleanliness.
The authorities should _____(12) into account the potentials of different categories of food for transmitting disease, and should set appropriate standards of control for the different categories - sellers of bottled drinks require less control than those of food. Dry foods, dried grains, and sugared foods are _____(13) likely to transmit disease than cooked rice, low-acid milk, egg, and meat products. _____(14), foods which are thoroughly cooked and eaten at _____(15) are safer than precooked food kept at high temperatures for several hours.
1 A for B on C by D at
2 A but B however C besides D moreover
3 A choice B processing C supply D production
4 A them B those C him D it
5 A and B or C but D yet
6 A soon B far C much D many
7 A services B kitchens C hygiene D foods
8 A hotels B houses C buildings D generals
9 A supported B enriched C contaminated D washed
10 A heavy B clear C high D poor
11 A to B about C from D around
12 A use B think C take D work
13 A highly B never C not D less
14 A Certainly B Interestingly C Surprisingly D Similarly