In natural language acquisition, single words serve as complete sentences in the 1: holophrastic stage 2: silent period 3: telegraphic stage 4: overgeneralization

To answer this question, the only thing we must do is to analyze the very definition of the two early processes involved in natural language acquisition:

Holophrastic stage:

it is the child's language acquisition stage where the acquiring of syntax is mostly done by utterances of single words.

Telegraphic stage:

it is the child's language acquisition stage where the infant start uttering multiple words in an early stage.

so, to answer the question, in natural language acquisition, single words serve as complete sentences in the:

1: Holophrastic stage

you   can   protest   and   boicot   and   have   marches  

verdadero

explanation: