已知f(x)=cosπx，x≤0f(x-1)+1，x＞0，则f(43)的值为 _

在相同温度和压强下，等质量的下列气体所占体积最大的是（　　）

A．H₂

B．O₂

C．CO₂

D．Cl₂

羧酸的四类衍生物中，化学性质最活泼的是（）。

A、羧酸酯

B、羧酸酐

C、酰氯

D、酰胺

商品的形象色是指不种类的商品包装在（）上有不同的要求

A、色彩

B、形态

C、材料

D、图形

The fridge is considered a necessity. It has been so since the 1960s when packaged food first appeared with the label: "store in the refrigerator. "

In my fridgeless fifties childhood, I was fed well and healthy. The milkman came daily, the grocer, the butcher, the baker, and the ice cream man delivered two or three times a week. The Sunday meat would last until Wednesday and surplus bread and milk became all kinds of cakes. Nothing was wasted, and we were never troubled by rotten food. Thirty years on, food deliveries have ceased, fresh vegetables are almost unobtainable in the country.

The invention of the fridge contributed comparatively little to the art of food preservation. A vast way of well tried techniques already existed—natural cooling, drying, smoking, salting, sugaring, bottling…

What refrigeration did promote was marketing—marketing hardware and electricity, marketing soft drinks, marketing dead bodies of animals around the globe in search of a good price.

Consequently, most of the world’s fridges are to be found, not in the tropics where they might prove useful, but in the wealthy countries with mild temperatures where they are climatically almost unnecessary. Every winter, millions of fridges hum away continuously, and at vast expense, busily maintaining an artificially cooled space inside an artificially heated house—while outside, nature provides the desired temperature free of charge.

The fridge’s effect upon the environment has been evident, while its contribution to human happiness has been insignificant. If you don’t believe me, try it yourself, invest in a food cabinet and turn off your fridge next winter. You may miss the hamburgers, but at least you’ll get rid of that terrible hum.

The statement "In my fridgeless fifties childhood, I was fed well and healthy. " (Line 1, Para. 2) suggests that ().

A．the author was well fed and healthy even without a fridge in his fifties

B．the author was not accustomed to using fridges even in his fifties

C．there was no fridge in the author’s home in the 1950s

D．the fridge was in its early stage of development in the 1950s

黄斑囊样水肿常见于（）

A.增殖型糖尿病性视网膜病变

B.视网膜色素变性

C.视网膜中央静脉阻塞

D.高度近视

E.白内障术后