以下哪一条不是CY3型液压机构建立不起压力的原因()
A.油泵低压侧有空气
B.合闸一二级阀阀口密封不严
C.高压放油阀未关闭
D.机构常高压管内有空气
参考答案:D
REVENUE FOR STORE X DURING WEEK 1
During week 1, revenue from eggs provided what percent of the total revenue for store X ?
试述建构主义关于教学的基本观点。