Solution
C

The number of matchsticks used for each of the digits 0 to 9 is $6,2,5,5,4,5,6,3,7$ and 6 respectively. Hence, the positive integers that can be made using exactly six matches are 6,9 , $14,41,77$ and 111. Therefore 6 different positive integers can be made.
11. Matchsticks can be used to write digits, as shown in the diagram. How many different positive integers can be written using exactly six matchsticks in this way?
A 2
B 4
C 6
D 8
E 9