绕火星做圆周运动的卫星的周期为T，离地高度为H，火星半径为R，则根据T、H、R和引力常量G，能计算出的物理量是（　　）

A．火星的质量

B．飞船所需的向心力

C．火星的平均密度

D．飞船线速度的大小

The government is to ban payments to witnesses by newspapers seeking to buy up people involved in prominent cases (21) the trial of Rosemary West.
In a significant (22) of legal controls over the press, Lord Irvine, the Lord Chancellor, will introduce a (23) bill that will propose making payments to witnesses (24) and will strictly control the amount of (25) that can be given to a case (26) a trial begins
In a letter to Gerald Kaufman, chairman of the House of Commons media select committee. Lord Irvine said he (27) with a committee report this year which said that self regulation did not (28) sufficient control.
(29) of the letter came two days after Lord Irvine caused a (30) of media protest when he said the (31) of privacy controls contained in European legislation would be left to judges (32) to Parliament.
The Lord Chancellor said introduction of the Human Rights Bill, which (33) the European Convention on Human Rights legally (34) in Britain, laid down that everybody was (35) to privacy and that public figures could go to court to protect themselves and their families.

A. since B. if C. before D. as