Final answer:
By the age of two months, a child should be able to hold their head up to 90 degrees and lift their chest.
Step-by-step explanation:
By the age of two months, an infant should be able to hold their head up to 90 degrees and lift their chest when placed in an upright position. This is an important milestone in their physical development. However, it is important to note that developmental milestones can vary slightly from child to child.