写出下面各数，并用“四舍五入”法改写成用“万”或“亿”作单位的数． 二百五十四万

局部义齿的后牙排列，应以恢复咀嚼功能为主，影响功能发挥的是（）

A.牙尖的高低

B.面沟窝的深浅

C.接触面积的大小

D.一定的解剖形态

E.人工牙龈距的大小

黑色素在隐球菌致病过程中的作用包括（）

A.可以引起血管梗死出血

B.可以引起组织纤维化

C.可以引起组织变性坏死

D.可以加强细胞壁的完整性

E.可以降低隐球菌对二性霉素B的敏感性

假定地球，月球都静止不动，用火箭从地球沿地月连线向月球发射一探测器。假定探测器在地球表面附近脱离火箭。用W表示探测器从脱离火箭处飞到月球的过程中克服地球引力做的功，用Ek表示探测器脱离火箭时的动能，若不计空气阻力，则 [ ]

A．Ek必须大于或等于W，探测器才能到达月球

B．Ek小于W，探测器也可能到达月球

C．Ek＝W，探测器一定能到达月球

D．Ek＝W，探测器一定不能到达月球

现值指数是指将按照一定的贴现率，把项目投产后各年的净现金流量折算为投资初始日的现值合计，然后与原始投资额进行比较得出的差额（）

Yellowstone Weather
Yellowstone National Park is at high altitude. Most of the park is above 7,500 feet (2,275 meters).
Yellowstone’s weather is unpredictable. In summer, it may be warm and sunny with temperatures in the high 70F. At night in any given month, the temperature may drop close to freezing. So it is best to come prepared for cold evenings and mornings, especially if you are camping or hiking. When you leave your campsite, please leave it prepared for possible thundershowers and wind.
A sunny warm day may become fiercely stormy with wind, rain, sleet and sometimes snow. Without enough clothing, an easy hike or boat trip can turn into a battle for survival.
Seasonal Weather Information
Spring
Cold and snow continue into May, although temperatures gradually climb Early in spring, daytime temperatures average in the 40F to 50F; by late May and June, they may reach the 60F and 70F. Nighttime lows fall below freezing.
Summer
Daytime temperatures are usually in the 70F, occasionally reaching the 80F in the lower elevations (高度). Nights are cool, temperatures may drop in the 40F and 30F—sometimes even the 20F. June can be cool and rainy; July and August tend to be somewhat drier, although afternoon thundershowers are common.
Fall
Weather can be pleasant, although temperatures average 10-20 degrees lower than summer readings. Nighttime lows can fall into the teens and lower. Snowstorms increase in frequency as the weeks go by or towards the end of the fall season.
Winter
Temperatures often stay near zero throughout the day, occasionally reaching high in the 20F. Subzero nighttime lows are common. Annual snowfall averages nearly 150 inches in most of the park. At higher places, 200 -400 inches of snow have been recorded.

If you are planning to spend your holidays in Yellowstone National Park in summer, what should you take with you.’

A．Just some light clothing such as T shirts or skirts.

B．Just some warm clothing such as sweaters and coats.

C．Both light clothing and warm clothing.

D．Either light clothing or warm clothin