Help with the present perfect subjunctive...

[ayúdame]

I'm trying to put this sentence into the present perfect subjunctive form. I know how to change the haber tense, but I'm having trouble with the second verb. For example, we're supposed to put what's in parentheses in the present perfect subjunctive form...

Es una pena que (haber aumentar) la contaminacion del aire en las ciudades grandes.

I know that here haber will change to haya, but I'm not sure how to conjugate the verb. Help?

[Rusty]

The present perfect is one of the tiempo compuesto forms of the verb. These are classified as having a helping verb ('haber'), followed by a past participle.

Only the helping verb is conjugated.

Does this help answer your question?

[ayúdame]

So aumentar in this sentence does not change?Just haber?

[Rusty]

It changes. When I explained what a compound tense is composed of, I said that the second part of the compound tense is a past participle.

You have two infinitives listed between the parentheses in your exercise. 'Haber', the (helping) verb, needs to be conjugated and 'aumentar' needs to be converted into a past participle.

[ayúdame]

So, would this be correct:

Es una pena que haya aumentado la contaminacion del aire en las ciudades grandes.

[Rusty]

Perfect, except there's an accent mark missing in your sentence.