观察心脏左心房早期增大应选择何种最佳位置并服钡剂检查（）
A.左前斜位相
B.右前斜位相
C.后前位相
D.卧位相
E.立位相
参考答案：B
Mother wanted to be a good provider, a role she _______ since her marriage to Father.
A．shoulders
B．has been shouldering
C．is shouldering
D．shouldered
当滚筒采煤机负载增加时，高压反而降低，这说明液压系统有漏损，泄漏处在主油路的低压侧，应停机处理。
