以下说法中正确的是（　　）

A．在光滑的水平冰面上，遥控玩具小汽车可以转弯

B．火车转弯速率大于规定的数值时，内轨将会受压力作用

C．汽车通过凹形桥时，凹形桥的半径越小或车速越高，车胎越易爆

D．汽车通过凸形桥时，汽车对路面的压力大小不断发生变化，总是小于汽车所受重力

Health officials in western Siberia are to begin in slaughter of thousands of birds today after identifying Russia’s first outbreak of a bird flu strain that can be fatal in humans. Doctors in neighboring Kazakhstan have also (1) that a 19-year-old poultry worker (2) admitted to hospital with (3) of bird flu, only to be diagnosed (4) double pneumonia.
The H5N1 strain of avian (5) has killed 60 people (6) 2fib in Vietnam, Thailand, Cambodia and Indonesia, but has rarely been found in birds or humans (7) Asia.
Health officials (8) that HSN1 is infecting migrating birds, which could spread the (9) into Europe. Earlier this year China registered the first outbreak of H5N1 (10) wild birds, some of which (11) to breeding grounds in Siberia. These birds could come (12) contact with others flying to Europe and North America.
Russia’s (13) began in the Novosibirsk (14) , about 1,750 miles (15) of Moscow in the Asian part of Russia, early last month, but the veterinary service (16) the virus only last week. Valery Mikheyev, the chief sanitary doctor of Novosibirsk, said that teams had been (17) the (18) birds and supervising the slaughter in13 (19) villages. He said, "The state of (20) of the inhabitants of these areas gives (21) cause for alarm. Up to 6,000 people are being (22) per day.
The virus seems to have (23) only private farms that let (24) mix with wild birds. Further outbreaks were registered in the Omsk and Altai regions, but the strain had (25) to be determined, Russia’s Emergency Situations Ministry said.