Because of the noise outside, Nancy had great difficulty in focusing on her experiment.

因为外面的噪音，Nancy很难集中注意力在实验上。

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Symptoms of eyestrain include sore eyes and difficulty focusing, poor night vision, difficulty in focusing after concentrating on an object, headaches and sore, red inflamed and weeping eyes.

眼睛疲劳的症状包括如下：眼睛疼痛，难于集中，夜视非常差，在注视一个物体后重新集中视线很困难，头痛，眼睛发红、疼痛、感染、流泪。

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They started out in school with higher levels of aggressive and disruptive behavior and more difficulty focusing and cooperating.

他们在学校中表现出强烈的好斗，很难集中注意力与同学合作。

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The new AF Focus Illuminator is a supplemental light included for those times when auto focus has difficulty focusing in dark places, or in scenes with particularly low contrast.

ENGADGET: Olympus Stylus TG-625 Tough adds AF light for tricky shots in rough situations