A month ago, the British government announced a plan to keep terrorist suspects indefinitely under house arrest (1) the home secretary’s say-so, It has been attacked from all sides ever since. This week the government backtracked. Under the Prevention of Terrorism bill, (2) to Parliament this week, house arrest would (3) a potential (4) in the government’s ever-expanding anti-terrorist arsenal, but the government would first have to (5) of Article 5 of the European Convention on Human Rights guaranteeing a right to liberty. Parliament would have to vote on that.The government could do this (6) the terrorist threat to Britain, already described by the government as " (7) ", got even worse. Even then, the powers would remain (8) by political and judicial safeguards. Before the home secretary could make a house-arrest order, he would have to be satisfied on the (9) of probabilities--no longer on the basis of "reasonable suspicion --that the suspect has been "involved in a terrorism-related activity". He would also have to be (10) that such an order was "strictly required". The period of house-arrest will be limited to a maximum of six months, extendable through a new house-arrest order. Within seven days of its being imposed, the High Court would have to confirm that the home secretary had " (11) grounds" for making such an order. Even if it were so satisfied, the case would go on to a full court (12) The bill also provides for a whole range of lesser restrictions including tagging, curfews, a ban on association with specified people, prohibitions on using phones, restrictions on travel, and so on. (13) to meet the threat (14) by each suspect and limited to a renewable period of 12 months, these would not be subject to the same judicial scrutiny as house arrest. Nor would they require (15) from the European convention.But the new orders, including house arrest, would be used only where a suspected terrorist could not be prosecuted (16) because the evidence against him was not admissible in court, or because it might (17) intelligence sources or (18) techniques. Charles Clarke insists that he would prefer to prosecute. (19) the home secretary is considering further anti-terrorist legislation, including making it (20) to be involved in the preparation or commission of terrorist acts. 19（）

A. unpracticed
B. unpredictable
C. unprepared
D. unprecedented