主要用于预防支气管哮喘的药物是（）

A.特布他林

B.氨茶碱

C.色甘酸钠

D.肾上腺素

E.异丙肾上腺素

Many people are wondering if it is safe to talk on the phone while driving. There have been quite a few accidents while drivers were talking on the phone. Some research is being done to find out if driving while talking on the phone is dangerous.
When there is a car accident police officers will find out if any of the drivers were using a cell phone. They will write this information in a report. The information will be saved and later studied.
There have been some very bad car accidents caused by drivers being distracted by cell phones. Drivers sometimes forget to watch the road carefully when they are using their phones. Not paying attention to the road can be dangerous, even deadly.
It is important for drivers to focus on the road. They need to pay attention to what is going on around them. They might need to stop or swerve quickly.
People want to make sure that the roads are safe for everyone. Studies will be done using the information police officers collect at accidents. Maybe someday this information will lead to laws about driving and using cell phones.

While driving, drivers must keep an eye on what is happening ______.

A．in other cars

B．on the phone

C．around them

D．at home