A．Cloud-to-ground lightning occurring in the U. S.
B．Types of lightning
C．Cause of lightning
D．Differences between thunder and thunderstorm
E Frequencies of thunderstorms occurring in the world and the U. S.
F Shock waves as thunder
Paragraph 4______

A. To limit the expenditure on drinking.
B. To restraint the development of beverage industry.
C. To lead people to drink less alcohol beverage.
D. To show government’s concern about public health.