How to choose between a present participle adjective and an adjective to modify nouns

[KelvinLi]

A free open-air concert on an international level, 'live 8' was an _ event.

A. inspirational
B. inspiring

I know the correct answer for the above question is "inspirational", but I don't understand why "inspiring" can't be used?

When it comes to choosing between a present participle adjective and an adjective to modify a noun, is there any general rule to follow?

I've read an article on the Internet, saying that a present participle adjective modifying a noun often indicates an on-going process, which somehow, explains why the word "inspiring" can't be used in the above question.

Am I right ?


Thanks,

Kelvin

[susiedqq]

Perhaps the verb will inspire you;

is inspiring

was inspirational.

[Pedroski]

Both are fine, who told you only inspirational is correct? Ask them why they would say that! I'd like to hear the answer!

was an inspiring/inspirational event.

明白？

[Tdol]

I would use inspirational because I feel that it is stronger and assume that is the effect the writer desired, but I agree with Pedroski that inspiring is not an error.