Sometimes when there is a big change in a young child or toddler's environment or daily routine, they will regress in the only way they know. This can occur in different situations such as toilet training or any kind of big move or change in their lives. It's not a learning disability because just because they regress doesn't mean there's anything wrong cognitively. It's also not a mental disability because regression is temporary. Autism also is not correct because regression isn't a diagnosis such as that but rather a stage a toddler or small child may go through while developing.
The sentence in which the adjective phrase or adverb phrase is best used to correctly maintain the meaning of the original sentences is D. Nicaragua has become a destination for adventurous tourists to visit. The other options don't even have these phrases.
