题干
Tom and his sister ______ to the barbecue last Saturday.They were very happy.
A：have invited
B：were invited
C：were inviting
D：invited
答案(点此获取答案解析）
B
Tom and his sister ______ to the barbecue last Saturday.They were very happy.
A：have invited
B：were invited
C：were inviting
D：invited
其化合物中不具有放射性的是（ ）