Answer :
D. 'Picking up the​ children, making afternoon​ snacks, and organizing outdoor activities are my jobs at the daycare center'is the correct answer.
Repetition of a chosen grammatical form or structure within a sentence is called a parallel structure. It is used to maintain balance and flow in a well-constructed sentence. Lack of parallel structure makes a sentence grammatically incorrect. In this sentence, picking, making and organizing are grammatical forms that are repeated to form the parallel structure.
The correct sentence is D. Picking up the​ children, making afternoon​ snacks, and organizing outdoor activities are my jobs at the daycare center.
A parallel structure implies using the same grammatical form or structure in a sentence. In D, "picking up + noun phrase", "making + noun phrase" and "organizing + noun phrase" are all used in the same grammatical structure. That is to say, the verb in its gerund form and a noun phrase following it.
