The organelle that has a subunit made of RNA is the ribosome.

Here's why:

* Ribosomes are the protein synthesis factories of the cell. They are composed of two subunits: a large subunit and a small subunit.

* Both subunits contain ribosomal RNA (rRNA), which is a type of RNA that is essential for the structure and function of ribosomes.

* The rRNA molecules within the ribosome help to bind mRNA (messenger RNA) and tRNA (transfer RNA) during protein synthesis.

So, while ribosomes are made of both RNA and protein, it's the RNA component (rRNA) that is crucial to their structure and function.