Match the events that contributed to the fall of the soviet union with the years in which they took place.
1- the soviet union invaded czechoslovakia and reversed its economic reforms.
2-workers in poland won higher wages after an uprising.
3-yugoslavia parted ways with the soviet union because of political differences.
4-military forces began constructing the berlin wall.
a- 1948
b- 1956
c- 1961
d- 1968

Here are the matches:

1- The Soviet Union invaded Czechoslovakia and reversed its economic reforms,  D.1968
2-Workers in Poland won higher wages after an uprising. B. 1956
3-Yugoslavia parted ways with the Soviet Union because of political differences. A. 1948
4-Military forces began constructing the Berlin Wall. C.1961

All of these events keep strengthening the west's relation with these countries and weakened Soviet Union's position even among its neighboring countries.