The mixture you separated was a mixture of iron filings, sand, and salt. Based on your understanding of matter, is this mixture a homogeneous mixture or heterogeneous mixture? How do you know? 
 Homogeneous mixture-the parts are not uniformly mixed
 Homogeneous mixture-the parts are uniformly mixed
 Heterogeneous mixture-the parts are uniformly mixed
 Heterogeneous mixture-the parts are not uniformly mixed