The most popular girl's name when I was born was Ashley.

("when I was born" is underlined)
a, independent clause
b. adverbial clause
c. adjectival clause ****
d. noun clause

adverbial

Thank you

It is not an independent clause and it is not an adverbial clause, therefore it must be a noun clause.

It states when, so then it would be an adverbial clause??

But adjectival clauses can begin with when. So please help me to understand. I thought that my first answer (adjectival clause) was correct.

The word "when" is normally introducing an adverbial clause. If it's used to introduce an adjective clause, it's unusual. Not impossible but unusual.

http://www.chompchomp.com/terms.htm
So which description among the grammar terms here does it fit?

Right

The correct answer is c. adjectival clause.

Explanation:
An adjectival clause is a type of subordinate clause that functions as an adjective, modifying a noun or prono

No. It doesn't modify any noun or pronoun.

Read up on subordinate clauses here:

http://grammar.ccc.commnet.edu/grammar/clauses.htm