世界卫生组织把铝确定为食品污染源之一．在下列应用中，不提倡使用铝的是（　　）

①制铝合金门窗 ②用铝箔包装食品③制炊具 ④制银色涂料 ⑤制相框 ⑥制电线．

A．③⑥

B．①⑥

C．②③

D．③④⑥

Observe that for the programmer, as for the chef, the urgency of the patron(顾客)may govern the scheduled completion of the task, but it cannot govern the actual completion. An omelette(煎鸡蛋 ), promised in two minutes, may appear to be progressing nicely. But when it has not set in two minutes, the customer has two choices—waits or eats it raw. Software customers have had (16) choices.
Now I do not think software (17) have less inherent courage and firmness than chefs, nor than other engineering managers. But false (18) to match the patron’s desired date is much more common in our discipline than elsewhere in engineering. It is very (19) to make a vigorous, plausible, and job risking defense of an estimate that is derived by no quantitative method, supported by little data, and certified chiefly by the hunches of the managers.
Clearly two solutions are needed. We need to develop and publicize productivity figures, bug-incidence figures, estimating roles, and so on. The whole profession can only profit from (20) such data. Until estimating is on a sounder basis, individual managers will need to stiffen their backbones and defend their estimates with the assurance that their poor hunches are better than wish derived estimates.

A．easy

B．difficult

C．simple

D．painless