如何进行奥氏体不锈钢焊接接头的均匀化处理？
参考答案：焊后将奥氏体不锈钢接头加热至850～900℃，保温两小时后空冷，使铬充分扩散到晶界，以消除贫铬区。
— What did you do yesterday?
— My brother took two friends of ______ to play chess with us. But I don't know ______ of them. [ ]
A. his; all
B. him; both
C. his; either
D. him; neither
人体维生素D主要来源于（）
A.皮肤合成的内源性维生素D
B.蛋黄中的维生素D
C.猪肝中的维生素D
D.人奶中的维生素D
E.牛奶中的维生素D
