Subject + 很 + 认真 / 认真 + 地 + Verb
The adjective 认真 (rènzhēn) means "serious" or "earnest" and describes a careful, attentive attitude. It can be modified by 很 as a predicate (他很认真) or used adverbially with 地 to describe how an action is performed. For example, 认真地听 means "to listen carefully."
他工作很认真,老板很满意。
Tā gōngzuò hěn rènzhēn, lǎobǎn hěn mǎnyì.
He works very conscientiously, and his boss is very satisfied.
你应该认真地听老师讲课。
Nǐ yīnggāi rènzhēn de tīng lǎoshī jiǎngkè.
You should listen carefully to the teacher's lecture.
她是一个认真负责的人。
Tā shì yí gè rènzhēn fùzé de rén.
She is a serious and responsible person.