In this study unit, a child is considered a toddler between the ages of

 A. one and two years.B. one-and-a-half and three years.C. one and one-and-a-half years.D. one-and-a-half and two years.

 My Answer is B 

I don't know what your study unit says.

However, according to these sources, your answer is wrong.

https://www.google.com/#q=toddler+age

Ok my answer is A

That seems to be the best answer.

To determine the correct answer, we need to understand the age range for a toddler. A toddler is generally considered a child who has just started walking and is around one to three years old. Let's review the given options:

A. According to Option A, a toddler is considered to be between one and two years old.
B. Option B suggests that a toddler is between one-and-a-half and three years old.
C. Option C states that a toddler is between one and one-and-a-half years old.
D. Option D proposes that a toddler is between one-and-a-half and two years old.

By comparing these options to the generally accepted age range for toddlers, we can determine the correct choice. According to the given options, Option B (one-and-a-half and three years) aligns with the commonly defined age range for toddlers. Therefore, your answer of Option B is correct.