鸡硒缺乏可引起脑软化、渗出性素质、白肌病、胰腺萎缩等。
参考答案：对
.
He was feeling bad. He went to work, _______, and tried to fix his attention on it.
A．however
B．so
C．although
D．while
直线制组织形式的缺点是专业分工差，( )。
A．机构简单 B．权力集中 C．横向联系困难 D．隶属关系不明确
