Form the union for the following sets. R = {10, 15, 20}

S = {20, 25}

R ∪ S =

{10, 15, 20, 25}
{20}
{ }
{10, 15, 25}

Iii-eneral sciencewhich of these is the best explanation of how a smooth round stone became smooth? a continuous freezing and thawingbvolcanic actioncit fell off the side of a cliffdit was in a stream for a long time.