I'm a beginner and am learning from CD (Pimsleur). There are two native speakers going through the dialogue. One, the man, pronounces が as I would expect - 'ga'. The other (female) pronounces it as ...
When is it correct to use は but not が, and when is it correct to use が but not は? Are there any times when you can use either without changing the meaning of the sentence? How does switching change ...