简述测频法和测周法测量转速的优缺点。

Accident Report Form

Accident	A car crashed into a tree. People were all trapped in the car.
Weather conditions	There was a heavy snow.
Date of call	December 3,2009
Time of call	9:30 pm
Name of caller	Mrs. Green
Place	Zhongshan Road, Harbin
Conditions of victims	Mr Green hurt his head. Mrs Green hurt her left leg. Their daughter felt terrified.
Action	Policement arrived at 9:40 pm and sent the victims to Gulou Hospital at 9:45 pm.

小题1:What time did Mrs Green call the police?
A.At 9:30 am          B.At 9:30 pm           C.At 9:40 pm
小题2:How many people were trapped in the car?
A.One                 B.Two                 C.Three
小题3:Whose left leg was hurt?
A.Mrs Green’s         B.Mr Green’s           C.Mrs Green’s daughter’s.
小题4:How was the weather that day?
A.It was sunny         B.It was snowy         C.It was rainy.
小题5:Which of the following is TRUE?
A.The car crashed into a wall.
B.The policemen arrived half an hour later and sent the victims to the hospital.
C.The car accident happened on Zhongshan Road in Harbin.