含有三个胚层组织成分的肿瘤称为
A．混合瘤
B．畸胎瘤
C．胚胎瘤
D．错构瘤
E．癌肉瘤
参考答案：B
---We can use QQ to talk with each other on the Internet.
---Really? Will you please show me it?
A．what to use
B．how to use
C．how can I use
D．what can I use
He found it increasingly difficult to read, ______ his eyesight was beginning to fail.
A. though B. for C. but D so
