与提高侧向分辨率无关的是()
A.电子聚焦
B.延迟线聚焦
C.探头频率
D.可变孔径
E.电子波束形成
参考答案:C
— You should have helped your mom wash the dishes.
—I meant .But she is always telling me to study.
A.to do
B.to
C.doing so
D.doing
简述皮亚杰认知阶段说的特点。