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:  
\[
\boxed{\text{All of these}}
\]