高致病性猪蓝耳病Ⅱ级疫情是指在（）日内，高致病性猪蓝耳病呈暴发流行，波及3个以上市地。
参考答案：14
When I came back yesterday evening, my brother ________ his homework.
A is doing B. has done C. was doing
分配阀的作用室有何作用？
