[33girl]

They are well aware they offered you a bid. You don't need to tell them. No matter how innocently it comes out of your mouth, it isn't going to sound good. If they bring it up in conversation with you (which I hope they have the smarts not to) just tell them you had issues with your classes at the beginning of the year that are now fixed and weren't sure you had time to commit to A sorority (not necessarily their sorority specifically). If you aren't interested, they will know that if you drop them during formal rush.

Above all, be polite and gracious when you go back to these chapters. But don't feign an interest you don't feel, if you don't feel it.