Researchers have concluded that young children typically possess the ability to acquire a second language with relative ease; however, adults typically require greater effort and time to master a second language. this is an example of a(n) period.

The correct answer is the critical period.

According to the critical period hypothesis, the time between childhood and adolescence is the perfect stage for acquiring almost a native-like competence in the second language.As a result, it would be much more difficult and it will require much more effort for an adult to learn a second language.

This hypothesis has been explained by means of biology and neuroscience. Furthermore, it is said one of the main factors of children and adolescents learning faster and easier than adults, is the plasticity of their brains.

the correct answer is d