You are always welcome, clive. Hehehe...I'm just giving you options or choices. Don't you know that there is nothing wrong with your sentence, Your sentence is good. What I'm trying to say is we are both participating in englishforums

M: I'm looking for a cheap flat close to the station? what do you mean this? I'm sorry, I hardly understand your sentence. Try this one: M: I'm looking for a cheap studio just near the (post station, gasoline station etc.).

It sounds better if we re-phrase the sentence. "The effects of global warming would kill millions of people if we won't listen to scientists.

Thank you Tyro, now I know what is right...

Somehow same as Eventually meaning you can learn this things later by practicing or learning.

Philip is right. An i s used before the words that begins with a vowel , A goes before all words that begin with consonants.

I just want to add a little bit but I am not confident if this answer is correct because I don't know totally the exact sentence" I went to the party, I was shocked when I saw everybody wearing in their weirdest costumes.!"

yeah it is the same... in some way not yet known or the thing must be done somehow. It is up to you how to use the two words in a sentence.