题干
He is a good student. He is ________ late for school.
A：often
B：usually
C：never
D：sometimes
答案(点此获取答案解析）
C
He is a good student. He is ________ late for school.
A：often
B：usually
C：never
D：sometimes
．如果再往盒中放进6颗黑色棋子，取得白色棋子的概率是
，则原来盒中有白色棋子【 ▲ 】
