A relative clause can be used to give additional information about a noun. They are introduced by a relative pronoun like 'that', 'which', 'who', 'whose', 'where' and 'when'. For example: I won’t ...
My best friend tests his 5 year old basic math questions from store-bought material which is good for one time use (his son memorizes the answers) …. but he wants to give him more practice.