Step 1: Understanding infancy
- Infancy is the earliest stage of childhood, and it is generally defined as the period from birth to the age of 2 years. This period is characterized by rapid physical and cognitive development.
Step 2: Analyzing the options
- (A) From birth to 6 months: While this period is crucial in infant development, it is not the entire infancy period.
- (B) From birth to 2 years: Correct. The period of infancy is typically considered to last from birth until 2 years, a time of rapid growth and development.
- (C) From birth to 5 years: This period overlaps with early childhood but goes beyond infancy.
- (D) 2 years to 5 years: This period refers to early childhood, not infancy.
Step 3: Conclusion
Thus, the correct answer is (B) From birth to 2 years, as this is the standard definition of the period of infancy.
\[
\boxed{\text{Correct Answer: (B) From birth to 2 years}}
\]