Oil and metals saw modest gains Thursday, but soybeans suffered their biggest loss in 40 sessions and sugar hit a seven-month low, deepening losses this week for many index-based commodity investors. The Reuters-Jefferies CRB index, one of the world's most popular commodity benchmarks, settled down half a percent. The 19-commodity index has fallen in every session since Friday, losing nearly 1.3% combined. Investors who track the CRB include