题目

Since he heard of his failure at the examination，Tom ________. A．had been very cast down B．has very cast down C．had very cast down D．has been very cast down   答案：D此题考查时态和语态。be cast down“使泄气”；since往往与现在完成时连用。句意是：自从他听到他考试失败以后，汤姆就非常沮丧。  11．方程组$\left\{\begin{array}{l}{ax+y=2}\\{2x+2y=3}\end{array}\right.$没有解，说明一次函数y=ax+2与y=x+$\frac{3}{2}$的图象必定（　　）A．相交B．平行C．重合D．不能确定