It is difficult to measure the success of the campaign at this stage.
在现阶段还难以估量这场运动的成败。
It is difficult to make oneself concentrate for long periods.
让自己长时间聚精会神是很困难的。
It is difficult to separate legend from truth.
传说与事实很难分辨。
It is difficult to define what makes him so popular.
很难解释清楚什么原因使他如此走红。
It is difficult to assess the full extent of the damage.
损失情况难以全面估计。
With so many variables, it is difficult to calculate the cost.
有这么多的可变因素，很难计算出成本。
It is difficult to find work in the present economic climate.
在目前这种经济大气候下很难找到工作。
It is difficult to understand the full import of this statement.
很难理解这份声明中的全部含意。
It is difficult to define the border between love and friendship.
爱情和友情之间的界线难以划清。
It is difficult to keep up with the rapid pace of change.
跟上迅速的变化是很困难的。
It is difficult to quantify an exact figure as firms are reluctant to declare their losses.
很难确定一个准确的数字，因为各家公司不愿公布它们的亏损情况。
It is difficult to make a comparison with her previous book—they are completely different.
这很难与她以前的书相比—两者是截然不同的。
It is difficult to sound natural or plausible.
这很难听起来自然或可信。
Once a biological control agent is released, it is difficult to control its speed.
一旦实施了生物控制手段，它的速度就很难控制。
It is difficult to isolate the factors that led to the next development—the emergence of urban settlements.
推动其进一步发展，即城市聚居点出现的诸多因素，是很难孤立出来看待的。
These methods may be useful for a while, but it is difficult to solve this problem completely.
这些方法可能暂时有用，但要完全解决这个问题是很困难的。
It is difficult to train pigeons to escape from a certain situation by pecking.
训练鸽子通过叼啄来脱离某种情境是很困难的。
It is difficult to attract young readers.
很难吸引年轻读者。
It is difficult to teach in such a short time.
要在这么短的时间内教学很难。
It is difficult to conceive of vigorous economic growth without an efficient transport system.
如果没有高效的交通系统，很难想象会有强劲的经济增长。
When a city's population grows by 5% a year, it is difficult to keep up.
当一个城市的人口以每年5%的速度增长时，基础设施很难跟得上。
You won't know what he means at first, for it is difficult to understand him.
起初你不知道他是什么意思，因为很难理解他。
With such a long interval, it is difficult to determine the age of this fossil.
时间隔得这么久了，很难确定这化石的年代。
Some people believe that it is difficult to protect users' privacy on social network sites.
一些人认为很难在社交网站上保护用户的隐私。
Targland's officials predict that these measures will be adequate, since it is difficult to collect the tortoises without a vehicle.
塔格兰德的官员预测这些措施将是足够的，因为没有交通工具的话，很难收集这些乌龟。
It is difficult to imagine how this could affect the cattle, but the relationship may help or hinder them in some way not yet recognized.
很难想象这会对牛产生怎样的影响，但这种关系可能会以某种未知的方式帮助或阻碍牛群的发展。
But if improving their hunting luck was the chief motivation for the paintings, it is difficult to explain why only a few show signs of having been speared.
但是，如果增强他们的狩猎运气是这些画的主要动机，那么就很难解释为什么只有少量画作有被长矛刺过的迹象。
It is also true that it is difficult to think of a single such system that has not, for better or worse, been substantially modified by human culture.
同样，很难想象一个这样的系统：不管是好是坏，都没有经过人类文化的实质性修改。
It is difficult to see how the theory applies to the plate between the Mid-Atlantic Ridge and the ridge in the Indian Ocean.
很难看出这个理论如何适用于大西洋中脊和印度洋脊之间的板块。
It is difficult to understand how reduced predation would lead to sudden increases in Acanthaster numbers in several places at the same time in specific years.
很难理解捕食减少是如何导致在特定年份的同一时间内，几个地方的棘冠海星数量突然增加。
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