等沉粒是沉降末速相同的颗粒。
参考答案：对
对风险厌恶者而言，无差异曲线表现为一条水平线。（）
—Do you know when Britain ______war on Germany during the Second World War?
—In 1993，I suppose.
A．announced
B．declared
C．fought
D．attended
