Law scheme applications for undergrad

Hi, I'm applying for first year schemes for commercial law and am being asked the question 'Why are you interested in Commercial Law?' repeatedly. I am genuinely passionate about commerce, and would've done a Business degree if not for law, but I don't know how to articulate that passion into an answer that these large, competitive companies would like to hear. I have no work experience in the Law industry, but I do have work experience for a marketing firm where I did content creation. Is there any way that I can incorporate this to form a competitive and impressive response?