The cup containing the sand and gravel is positioned (it could be held by a classmate or a ring and ring stand) above a clean cup while the dirty water is poured through.
(The cup; containing; the sand and gravel) (The cup containing the sand and gravel; is positioned; it could be held by a classmate or a ring and ring stand) above a clean cup while the dirty water is poured through) (it; could be held; by a classmate or a ring and ring stand; T:while the dirty water is poured through) (the dirty water; is poured; through)
The cup The cup containing the sand and gravel it the dirty water
containing is positioned could be held is poured
the sand and gravel
it could be held by a classmate or a ring and ring stand) above a clean cup while the dirty water is poured through
by a classmate or a ring and ring stand T:while the dirty water is poured through
through