Chris McKhann , analyst at OptionMonster.

Crude oil is nose-diving today, but options buyers have moved in on the drop.

The United States Oil Fund ( USO) is down more than 7% today, trading at $27.37. The drop mirrors the fall in the commodity itself, but while the actual futures remain within the recent range, the ETF is now down to its lowest levels since March 16. The futures are 45% off of their February low, while the U.S. Oil Fund is only 20% higher than its low.

In the midst of this drop, OptionMonster's tracking systems are showing heavy action in the July 28 calls, where more than 16,000 contracts have changed hands, the majority of them purchased even as the price has dropped from $2.90 to $2.65. The open interest at that strike is just 2,699 contracts, indicating fresh opening positions.

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