题干

下列过程中一定发生化学变化的是(    )

A:气球膨胀

B:海水晒盐

C:矿石粉碎

D:燃放鞭炮

上一题 下一题 0.0难度 选择题 更新时间:2010-05-12 01:41:56

答案(点此获取答案解析)

D

同类题1

阅读理解

    Of all nature's disasters, forest fires are often considered the most frightening. Moving at lightning speed, huge walls of flames can burn acres of land in just a few minutes. And although technology, including the use of fire-retardant chemicals, has greatly helped the fight against forest fires, they still do great damage.

    According to the National Interagency Fire Center, the fire season last year was the worst on record in terms of the number of fires and acres burned. There were 96. 385 fires and 9.873429 acres affected by fire in a year that was 125% more destructive(毁灭性的) than the10-year average. These fires cost the federal government $1.5 billion to fight, and this figure does not include the money spent by local and state governments as part of the effort.

    Fires in the southern states represented half of the national total last year with Texas, Oklahoma and Arkansas being home to a usually high amount of activity. Wildfire has also taken place in Western states such as California, Colorado and Alaska throughout the past 10 years.

    It is said that two-thirds of forest fires are started accidentally by people. Almost one quarter are purposely set, while lighting causes 10%.

    Forest fires can have advantageous effects. Charcoal(木炭) enriches soil and some plant species(种类) grow well after fire. The cones of the jack pine tree, for example, will not spread their seeds unless there is heat. Douglas fir trees grow best in open sunlight areas after fire.

同类题4

现代文阅读

外婆家的端午节(改编)

    ①如今不是看到满街的粽子,商场中的打折,电视中的活动,我已经感觉不到它——端午的存在。每次念到“端午”这两个字时,不由地让我想起小时候在外婆家过的端午节。

    ②一盏昏黄的豆油灯,一张脱了朱漆的梳妆台,一方古旧的镜子。背影 中一个老人在镜前动作迟缓但一丝不苟地梳头,不一会儿她就梳好了,纨了一个盘髻。这时她不知从哪里拿出的一朵绢花,粉红的,端详了很久,她轻轻地插在头上。我睡眼蒙眺地看着她,我的太姥姥。

    ③一切收拾好了,她走到床前做了个动作示意我睡觉。我闭上了眼睛,但能感觉到灯灭了,咯吱的一声关门。之后就是一阵静谧,我知道在艾草还没有插 上门楣时家里谁都不可以说话,要不然不吉利,我也绝对不可以出声,这是大人们交代过很多次的。静,真静!

    ④“小乖乖,起床了,太阳都晒屁股了!”我在姥姥那熟悉的叫喊声中坐起来。穿上姥姥给我做的那双绣着仙桃的红布鞋,我出了卧室。这时候太姥姥正坐在堂屋里。“太姥姥好。”说完,我便跪了下去磕了三个响头。“乖,拿着纳福篮一边玩去。” 她笑吟吟地拿起身边那只漂亮的八边形布篮给我。

    ⑤姥姥拉我到门外,洗脸盆里已注满了清水。洗了手和脸,我拿了几根艾草学着姥姥的样子在房屋里的每个角落里都扫一扫,一边扫还一边说:“端午节扫一扫,蚊虫蚂蚁都往外面跑。”

    ⑥早饭,一个粽子,一个鸭蛋,一碗粥,匆匆吃过。吃完后姥爷便用雄黄在我头上画了一个“王”字,据说这样那些鬼蚁蛇虫都不会伤害我。

    ⑦“张奶奶好。”“李奶奶好!”吃完饭不能闲着,拿着太姥姥送给我的小篮便挨家挨户地窜门,老人们都纷纷拿些零食往我小篮里放。不知何时小篮满了,我便回到姥姥家,也中午了。

    ⑧“快洗手吃饭!”不知什么时候,爸爸妈妈和姐姐已经站在门口了。满桌子的饭菜都上齐了,雄黄酒也端上了。父亲和太姥姥都坐在上席——在老家姑爷是客, 应该坐上席。姥爷坐在父亲身边,别人都可以乱坐。“吃吧。”太姥姥动了第一筷子之后我们才开始动筷,“来吃鸡腿,跑得快快的。”太姥姥第一筷子是给我和姐姐。“姥姥你也吃。”坐在太姥姥身边的父亲也挑了一块肉给太姥姥。然后呢,姥爷给父亲夹菜,姥姥给妈妈夹菜,妈妈再给姥姥夹菜;姥爷给父亲倒酒,父亲给姥爷敬酒。一家人其乐融融,客堂内充满了欢声笑语……

    ⑨因为姐姐明天还要上学,妈妈他们今天得回家。到了分别的时候,我实在不 舍就拉着妈妈的衣服。姥姥见状就说李奶奶家的小牛刚才掏了好大一窝鸟,现在正在分小鸟,再不去就没有了。”我一听松开手就往李奶奶家跑,当然没什么小鸟,倒是有很多的小孩在玩过家家,我便加入其中,一直到吃晚饭。

    ⑩月,轻轻地爬上了那棵老槐树上。姥姥搬了凉床到院子里,我躺在床上,姥姥摇着蒲扇给我扇风赶蚊,讲着那古老的牛郎织女。太姥姥在屋中纺线,吱吱呀呀。我迷迷糊糊地睡着了,依稀中还听到吱吱呀呀的声音。