Question

(The children built a sandcastle )
while their father read a book.

adverb
adjective
subordinate
independent

Answer 1

Clause- has subject and verb
Independent- could be a sentence on its own.

Answer 2

So then it would be independent clause since The children built a sandcastle can stand on its own? @douglaswinslowcooper

Answer 3

Just so. Good.

Answer 4

Thank you.:)