, ,
( 2 60 , A
BCD
1. _______
A B
C D
2. S
B _____
A S=B B S=2B C S=B/2 D S=1/B
3. ______
A B
C D
4.OSI/RM ______
A B
C D
5. _____
A
B
C
D
6. ___
A B
C D
7. ______
A B C D
8. _____
A B C D