Assertion: ribosomes are non membrane bound organelles found in prokayotic cells only.
Reason:these are present only in cytoplasm.

Dear student,
Please find below the answer:

Both Assertion and Reason are false.

Ribosomes are non-membrane bound organelles found in both prokaryotic and eukaryotic cells. They are made up of ribonucleic acid and protein molecules. They maintain their structure by chemical interactions between these components. 

They are found in the cytoplasm as well as in chloroplasts, mitochondria and in association with the endoplasmic reticulum.

Hope this clears your doubt.
Regards.