What does syntax in toddler-hood typically involve?

The correct answer highlights a key developmental milestone in toddlers' language acquisition. During toddlerhood, children begin to communicate using two-word combinations, which are fundamental in showing their growing understanding of syntax. These two-word utterances typically consist of the most pertinent words that convey essential meaning, for example, combinations like "want cookie" or "more juice." This ability demonstrates their capacity to prioritize significant concepts and construct meaning from their surroundings, which is a critical step in the development of more complex sentence structures later on.

Focusing on the other options: While option A mentions simple declarative sentences, toddlers usually are not yet reliably producing those and typically rely on more basic forms of expression. Option C suggests an internal cognitive process that isn't clearly observable in toddlers, as their utterances are straightforward and often lack the complexity described. Option D relates to a stage where children can use longer utterances, which typically occurs later, as toddlers initially focus on shorter, more immediate expressions. Therefore, option B accurately encapsulates the essence of syntax development during toddlerhood, emphasizing the use of important words in meaningful combinations.