RELATIVE CLAUSE with PREPOSITIONS
Her many friends gave her encouragement. I like to be considered among them.
Her many friends, among whom I like to be considered, gave her encouragement.
Her father died last year. She looked after him for over twenty years.
Her father, whom she looked after for over twenty years, died last year.
The bed has no mattress. I sleep on this bed.
The bed on which I sleep has no mattress.