In my point of view, One Room can be associated with only one Lease at a time since a room can only be assigned to one student at a time (for the semester). Lease document is a legal document and only one lease agreement can be valid during a time. hence in my perspective option(d) is also correct. Kindly guide.

We're in the same boat.

yes I think the same. i choose the same answer and cant think why option c was chosen.

Imagine a database and I ask you to find information on room "1234" in the past two years. That room is supposed to be on multiple lease documents in the database to get information about who leased that room. This is the same as leasing a house. A house can on multiple contracts (though on one contract at one time).