SharePoint 2010 Designer Workflow

1)I have a designer workflow with two conditions like multiple and single as selections e.g. 'Single' and 'Multiple'.

2)There are some options with check boxes below the selections e.g. A , B , C and D.

3)If the user selects 'Single' as option and selects the check box A below, an email will be sent to the A and subject saying "User selected A and here is you what to do"

4)If he selects 'Multiple' as option and selects B and C, an email should be sent to both B and C saying "User selected B and C and here is what you need to do"

I was able to send mails in both cases but am unable to make how to mention two check boxes B and C in subject when they select multiple selection as option.

Please help me out in this scenario.