高效液相色谱梯度洗脱中的低压梯度又称内梯度，高压梯度又称外梯度。
参考答案：错
解析：低压梯度又称外梯度，高压梯度又称内梯度。
Mother asked the youngest kid _______with his toy car．
A．what the matter was
B．what was the matter
C．what the matter is
D．what is the matter
混凝土芯样试件抗压强度代表值应按一组三块试件的最小值确定。
