题干
The children ＿＿＿＿＿＿ very quiet； I wonder what they ＿＿＿＿up to.
A：were； are being
B：are being； are
C：are； do
D：are being； do
答案(点此获取答案解析）
B
A：were； are being
B：are being； are
C：are； do
D：are being； do
