Выпишите то предложение в котором глагол сказуемое представляет деянье как факт.

The sons of the manager work in agriculture on the native land.

The predicate work is used in the Present Simple to expresses the fact of employment. It means that the sons of the manager have a job in the agriculture company registered in the country where they were born.

Predicates of the other two sentences the indicate the activities.

Has harvested the crops means finishing the work of gathering the crops and as the results the crops are in the barn (Present Perfect).

Are helping in the construction means being in the process of doing some construction works (Present Continuous).