I was told that there were about 50 foreign students ________ Chinese in the school, most ________ were from Germany.

A．study; of whom

B．study; of them

C．studying; of them

D．studying; of whom

下列各组物质间可能包括多步反应，其总的离子方程式正确的是 [ ]

A．向NaClO溶液中通入过量SO₂: ClO^-+ SO₂+H₂O =HClO^-+HSO₃^-

B．向AlCl₃溶液中投入过量Na: Al³⁺+4Na+2H₂O= AlO₂^-+4Na⁺ +2H₂↑

C．向FeBr₂溶液中通入少量Cl₂: 2Fe²⁺+4Br^- +3Cl₂ =2Fe³⁺ +2Br₂ +6Cl^-

D．向明矾溶液中滴加Ba(OH)₂溶液，恰好使SO₄^2-沉淀完全:

2Al³⁺+3SO₄^2-+ 3Ba²⁺+6OH^-=2Al(OH)₃↓+3BaSO₄↓