天然气的热值有两种，即（）和冷热值。

丙氨酸的R基为-CH₃，谷氨酸的R基为-CH₂-CH₂-COOH，它们缩合形成的二肽分子中，C、H、O的原子个数之比为[ ]

A．7：16：6

B．7：14：5

C．8：12：5

D．8：14：5

下列各句中，加点的成语使用恰当的一句是

A．你们到北京去的事，让我去找领导也没有用，因为师出无名，让他怎么批呢？

B．除了银河系星星以外，河外星系里还有无数的星星，真是不胜枚举。

C．一个烟头引起了一场大火，这座被烧毁的大楼让人叹为观止，唏嘘不已。

D．李校长既抓教学，又抓体育，经常察看寝室，深入食堂，对学生关怀无所不至。

要对已入围供应商的交货准时率、到货率、商品质量和售前售后服务进行经常性考核。

是管理的重要职能，根据组织的规模和任务设计组织结构和相应的职责、任务和权力，以及建立健全各项规章制度等（）

A.计划职能

B.组织职能

C.人员管理

D.领导职能

E.控制职能

Press Photographers

Good press photographers must have an "eye" for news, (26) journalists must have a "nose" for a good story. They must be able to interpret a story and decide rapidly how they can take (27) of the best opportunities to take pictures. The most difficult part of a press photographer’s job is that he or she has to be able to (28) a complicated situation with just one photograph. They rarely have second (29) and must be able to take the required (30) very quickly. Indeed, speed is essential — if the photographs are not (31) for the printing deadline, they are very unlikely to be of any (32) .
Most press photographers begin (33) with a local newspaper. There, the (34) is mostly for material of regional interest. Photographers may be expected to photograph a lot of unexciting events but to (35) the enthusiasm to put "something special" into every picture.
There is (36) competition among those who want to move from local to national newspapers. Here, the work is much more centered on news. The photographer must work (37) greater pressure and (38) more responsibility. Only (39) reliable, talented and resourceful photographers (40) this difficult move. The work is tough and can be (41) . On an overseas assignment, photographers may have to (42) unfamiliar food and accommodation, physical and mental stress, and (43) difficulty in transporting the pictures from an isolated area to get them to the newspaper (44) They also have to (45) the competition from other publications.

A. essentialB. availableC. varied D. dangerous