Infants around 2 to 3 months of age are capable of producing open vowel sounds. These sounds are examples of

The correct option is cooing.

During the first year of life, infants progress through several key stages of pre-linguistic and linguistic development:
1. Cooing (2 to 3 months): This stage consists of producing soft, open vowel sounds (such as "oo", "ah", or "ee"). These are the child's first vocalizations beyond crying and represent early control over the vocal tract.
2. Babbling (around 6 months): This stage marks the introduction of consonant sounds combined with vowels, resulting in repetitive syllables like "ba-ba" or "da-da".
3. One-word utterances (around 12 months): Infants begin to produce single, recognizable words with specific meanings (e.g., "mama" or "ball").
4. Shouting: This refers generally to loud vocalizations that can occur at any stage but is not a defined linguistic milestone.

Therefore, the open vowel sounds produced by infants at 2 to 3 months of age are examples of cooing.