I have a question. <br/><br/>"The ancient Greeks, who posted sentries at their temples to make sure those who entered did<u> so</u> right foot first, so as not to offend the gods."<br/><br/>Can I omit 'so' in the above sentence?<br/><br/>If it is acceptable, what is diffrent between before and after?<br/><br/>Many thanks in advanced.