Got boards tomorrow and I was going through some past years paper and one question stumped me. The leader counted _______ the cooperation of his colleagues. On/Upon both sound equally correct but I am not sure. Could someone please tell me the correct answer and also explain when 'on' is used and when 'upon' is.
The meaning of "upon" is very similar to "on", but it tends to be used in more formal language, and when the meaning is more abstract.
He put the hat on his head. (simple)
The bishop reverentially placed the crown upon the king's head. (formal)
Spring is nearly upon us. (abstract)
In the particular example you give both "on" and "upon" could be used. As the meaning is quite abstract, and the style is fairly formal, using "upon" may be a good choice. But "on" should also be marked correct. There is no error in using "on".