A year later，with the nation’s economy ________，Bush’s approval rating dropped below 40 percent
B
introuble：陷入困境。由于经济陷入困境，所以支持率下降了很多，符合句意。
Thefarmingmethodshavebeen________improvedwiththeinventionofthenewmachine.
Sincewehaveafocusedsubject，weshouldnottalk________.