Final answer:
First words in children are usually understood around one year of age. This is the period when they are typically expected to say their first meaningful words and understand simple commands. The exact timing can vary, but in general, this significant milestone in language development occurs near the first birthday.
Step-by-step explanation:
Understanding when first words are usually understood in children involves examining various stages of language development. Most babies start showing signs of communication from a very early age. Starting before birth, babies are already beginning to develop language and communication skills. At about 6 months, a baby is likely to enjoy vocal play and may start making recognizable syllable sounds such as "mama" or "dada". However, these early vocalizations might not convey specific meaning.
As babies approach their first birthday, they typically enter the "one-word" stage of language development. During this stage, children understand and can produce single words that often pertain to familiar objects or events, usually nouns. A child in this stage might say "cookie" to either identify or request a cookie. By 12 months, babies may be saying their first meaningful words.
When considering the specific age at which first words are generally understood, our references clearly indicate that this occurs around the one-year mark. Other milestones, such as sitting, standing, crawling, and responding to simple commands, also occur around this time frame.
Therefore, the answer to when first words are usually understood is option "b. one year." It is important to note that while some children may exhibit early signs of communication, such as babbling or cooing, true word understanding typically coincides with the first birthday. This is a key period in a child's life when they not only begin to verbalize but also start to comprehend the meaning of words and instructions provided to them, signaling a vital step in cognitive development.