The nurse notes that an infant stares at an object placed in his/her hand and takes it to his/her mouth, coos and gurgles when talked to, and sustains part of his/her own weight when held in a...

The nurse notes that an infant stares at an object placed in his/her hand and takes it to his/her mouth, coos and gurgles when talked to, and sustains part of his/her own weight when held in a standing position. The nurse correctly interprets these findings as characteristic of an infant at which of the following ages?

1. 2 months.

2. 4 months.

3. 7 months.

4. 9 months.