6.
Your Answer is
Correct Answer is H
Explanation
Item H: The past participle of designed is used as a post-attributive and modifies kiln.
Item F/G: Before the underlined part is a complete sentence, and the underlined part is not guided by a conjunction, so it cannot be a complete sentence after it.
Item J: As a countable noun, Brick needs to add the article a/the to satisfy grammatical correctness.