L220

He must not allow this unusual barrier （obstacle） to stop him from fighting against the enemy.
他绝不能让这个不寻常的障碍阻止他同敌人作战。

Next semester, Susan must take three compulsory（required） courses.

Should either of these situations occur, wrong control actions might be taken and a potential accident sequence initiated.（started）
如果发生上述任何一种情况，可能会采取错误的控制行动，并引发潜在的事故。

Now about half of the women who work in social welfare （well-being） are part-time, as compared to 38% in the private sector.

It is not clear whether the increase in reports is stemmed （originates）from greater human activity or is simply the result of more surveys.
目前尚不清楚报告的增加是由于人类活动增加还是仅仅是更多调查的结果。
This is the sort of case in which judges must exercise the arbitrary power described a moment ago.
在这种情况下，法官必须行使刚才所述的专断权力。

Floods have undermined （spoiled） the foundation of the ancient bridge.
洪水破坏了这座古桥的地基

A frequently cited （mentioned ）example of the endangered species is the panda.
一个经常被引用的濒危物种的例子是熊猫。