Don't be angry with us. We ________ with
题型：选择题
问题：
Don't be angry with us. We ________ with you together, but we were busy with our final reports when you called in.
A．would eat out
B．must have eaten out
C．should eat out
D．could have eaten out
题型：选择题
某实验小组的同学为了测定实验室中氯酸钾样品的纯度，取一定质量的该样品与1g二氧化锰混合，其总质量为6g。依次加热该混合物t1、 t2、t3、t4时间后，分别冷却称量剩余固体质量，记录的有关数据如下表（样品中的杂质不参与化学反应）：
试计算：
(1)完全反应后产生的氧气的总质量为______；
(2)样品氯酸钾的纯度是多少？