Answer:
normal behavior because of Brian's age.
Step-by-step explanation:
The development of empathy in a child is a question of debate. Many theories suggest that a child develops empathy at the age of two. So, when parents see their child not behaving empathetically, they get worried. But some children tend to develop empathy after two years of age.
In the given case, Brian's laughing when his sister is crying is normal for the children of Brian's age. Knowing the meaning of empathy is too early for him. Brian will develop empathy as he will grow and learn the meaning of emotions.
So, the correct answer is that its normal behavior for the children of Brian's age.