GMAT Sentence Correction (SC) | Re: Congress is debating a bill requiring certain employers

Actually now I know why,

so that makes it clear who "they" is referring to.

eg:

Use "so as" if there is only one noun which can be modified by "so as".
Ex. Jim worked hard so as to get promotion.[promotion is only for Jim]
Use "so that" if there are more then one noun, then go for "so that"
InCorrect: Jim divorced Jeniffer so as to marry.[Notclear: who wants to marry]
Correct: Jim divorced Jeniffer so that he could marry.[Clear: Jim wants to marry]