税收的三大要素是（）。
A.纳税人
B.纳税环节
C.税率
D.征税对象
参考答案：A, C, D
It was with great joy _____ he received the news that his lost daughter had been found. [ ]
A. because
B. which
C. since
D. that
araC蛋白既可作为激活蛋白，又可作为阻遏蛋白起作用。 ( )
