 Re: conditional sentence
It's not a matter of can you / can't you. And nothing to do with idiomatic language. If and Even if have two completely different meanings and are therefore used in different contexts. The meaning of the sentences changes completely if you substitute them.
If = on the condition that X, then Y.
If you get good grades, you should find a job easily.
If you'd been there, you would have been able to stop them
Even if = whether X or not, then Y.
Even if you get good grades, you'll have no chance of finding a job.
Even if you had been there, you'd never have been able to stop them.
So no - they're not alternatives, but for reasons of meaning, not grammar. |