时间序列分析主要用于系统描述、系统分析和（）
A．预测未来
B． 系统集成
C．功能描述
D．预测描述
参考答案：A
There ____ a terrible accident then, ____ three passengers were killed and twenty were injured as well.
A．was occurred; which
B．was occurred; in which
C．occurred; which
D．occurred; in which
早期胃癌包括（）
A．黏膜内癌
B．黏膜下癌
C．侵及肌层的癌
D．侵及浆膜层的癌
