Step 1: Meaning of liquid assets.
Liquid assets are those current assets which can be easily converted into cash without significant loss of value.
Step 2: Examples.
- Bills Receivable = short-term promise to pay, easily realisable.
- Debtors = amounts receivable from customers, part of liquid assets.
- Cash = already liquid.
Step 3: Conclude.
Thus, all the given items (BR, Debtors, Cash) are liquid assets.
Final Answer:
\[
\boxed{\text{All of these}}
\]