Answer:
85%

Explanation:
To find this whole question out, let us make all numbers percentages:
percent
percent
percent
Now let us start with the number order:
4/5 is 80 percent, which is the lowest number in the entire group:
80%
5/6 is 83.33 percent which is the second lowest number in our group:
80% , 83.33%
85% is the third lowest:
80% , 83.33% , 85%
0.9 is the greatest, equaling to 90%:
80% , 83.33% , 85% , 90%