问题: how to translate “**上课时注意力不集中”？
解答:
It's better to say:
I can't concentrate during the class.
You can also use "in the class", but not "on the class".
"Concentrate on sth" is valid, but not "on my class".
Other ways to translate:
I can't focus myself in the class.
I can't keep myself focused in the class.
I can't keep my mind focused in the class.
I can't keep my mind concentrated in the class.
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