$3.$ An auditor is testing the operating effectiveness of a key control activity. He expects one deviation and determines he can tolerate three deviations in order to rely on the control for purposes of planning his substantive testing procedures. He selects $50$ items for testing and notes two deviations during testing.

What is the sample deviation rate for this control? A$.1\%$ B$.2\%$ C$.4\%$ D$.6\%$