的过去式

There are two findings summarized from previous studies:(1) the least squares estimator is a common choice of researchers, but under an unequal probability design, the estimator is biased,(2) the probability weighted estimator is consistent but may have a large variance.

过去的研究发现：(1)在不等机率抽样时，一般常用的最小平方法所得到的回归参数估计式并非不偏估计式；(2)机率加权最小平方法可以改善不偏性，然却增加估计的变异程度。

His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.

我记得很多老师讲过去完成式的时候说这个时态用在一个过去的事情发生在另一个过去的事情以前的时候用，按照此理容易选A 因为

Person pork search enhanced interactive function, in letting everybody can participate in its, community of the relation that the network news that becomes traditional searchs humanness to look for person, person to ask person, person touchs person, person to squeeze person, person to endure a person network is interactive activity, change the dot in the past is one-way to choosing form the search is opposite for present dot group, group bit righter, group pair of open mode searches of group of type, become as dry as a chip insipid inquiry process quizs for one person, all directions is responded to, one stone arouses 1000 billow, one call sleep lightly 10 thousand open-armed human nature turn search experience.

人肉搜索增强了互动功能，让大家能够参与其中，变传统的网络信息搜索为人找人、人问人、人碰人、人挤人、人挨人的关系型网络社区互动活动，变过去的点对点式单向搜索为现在的点对群、群对点、群对群式的开放式搜索，变枯燥乏味的查询过程为一人提问，八方回应，一石激起千层浪，一声呼唤惊醒万颗真心的人性化搜索体验。

In West Germanic, the 2nd person preterite indicative ending -''t'' is restricted to

在西日耳曼语言里，以-''t''结尾的第二人称过去直陈式只存在於「过去─现在时」动词里。

Everything about her had been smooth and definite, even the tones of her voice and the way her light brown hair, which she wore a la Pompadour*, was rolled stiffly back from her forehead and coiled in a burnished rope on the top of her head.

她的一切都是那么安详平淡，那么不事张扬，甚至包括她说话的声调和她选择的发式；她梳的是高卷式发型她梳的是高卷式发型，甚至包括她说话的声调和她选择的发式她梳的是高卷式发型，淡褐色的头发从前额向后紧紧地卷过去用一根光亮的头绳盘绕在头顶上那是一个凡事都严肃认真的年代，的头绳盘绕在头顶上。

Indeed Skyjack abandoned its venerable differential drive system on its 68RT line to make an RT scissors with 32 feet of platform height, for example, retract down to a 69-inch stowed height.

商业建筑的诱惑力非常大，以致于大多数主要剪式升降机制造商- Genie、Haulotte、MEC和Skyjack都在过去的18个月里引入了新型RT剪式升降机。

Village life is portrayed as sequestered in a bygone age, with farmers trailing water buffalo through postage-stamp paddies and rural labourers trudging home in the twilight from Dickensian factories.

在过去的年代，乡村生活被描述成世外桃源式的生活，农民牵着水牛穿过一块块稻田，黄昏下，乡村工人从狄更斯式的工厂里蹒跚地走回家。

To say what you wish about the past , you use the past perfect

要表达对过去的希望，用过去完成式

The past perfect is an action in the past that occurred before a separate action in the past.

过去完成式就是在过去某个时间发生的事情之前所发生的事情。

S+ Ved ... after S had p.p.

过去完成式是用在两个过去发生的动作有先后顺序时

In the United States, chronic alcoholism and hepatitis C are the most common ones.

在美国，慢性酒精中毒，肝炎是最常见的。

If you have any questions, you can contact me anytime.

如果有任何问题，你可以随时联系我。