The boy who ate all cake was panished
the cat who cried all night continued to cry in the morning
the neighbor whom <span>you need to talk to
the kid whom you meet last mondey
там точно what а не that?
this is exactly what i need to tell you
</span>These are the keys that<span> open the front and back door.</span>
the car what need to me, has stolen.
Do you know the boy whose<span> mother is a nurse
</span>do you like my boss whose all clothes are black as men in black?
<span>which are the best vegetables for long keeping
</span>i'm making the conference in moscow, which ended on mondey
Потому что это герундий. Иногда перед герундием может стоять предлог, в данном случае "by playing" означает "проигрывая" (деепричастие) или "путем проигрывания".