在进行项目活动历时估算时，（）属于参数估算

A、从以前类似计划活动的时间持续时间为依据来估算

B、用需要完成工作的数量乘以完成单位工作所需时间作为估算活动时间的依据

C、利用最有可能的历时估算，最乐观的历时估算和最悲观的历时估算来计算

D、利用以历时信息为依据的专家判断来估算

Did you ever have someone’s name on the tip of your tongue and yet you were unable to recall it (1) this happens again, do no (2) to recall it. Do something (3) for a couple of minutes, (4) the name may come into your head. The name is there since you have met (5) person and his name. It (6) has to be dug out. The initial effort to recall (7) the mind for operation, but it is the subconscious (8) that go to work to dig up a (9) memory. Forcing yourself to recall (10) never helps because it doesn’t (11) your memory；it only tightens it. Students find the preparatory method help (12) examinations. They read over the questions (13) trying to answer any of them. (14) they answer first the ones (15) which they are most confident. Meanwhile, deeper mental activities in the subconscious mind are taking (16) ; work is being done on the (17) difficult questions. By the time the easier questions are answered, answers (18) the more difficult ones will usually begin to (19) into consciousness. It is often (20) a question of waiting for recall to come to the memory.

20（）

A.nearly

B.likely

C.just

D.even