影响土壤微量元素有效性的因素是（）、（）、有机质、土壤质地。
参考答案：酸碱度;氧化还原电位
如图所示，重为5N的木块A，在水中处于静止状态，此时绳子的拉力为3N，木块所受浮力的大小和方向是（ ）
A．8N，竖直向上
B．5N，竖直向下
C．3N，竖直向上
D．2N，竖直向上
When I talked with my grandma on the phone, she sounded weak, but by the time we （）up, her voice had been full of life.
A. were hanging
B. had hung
C. hung
D. would hang
