is classified as a ‘pre-noun adjectival’ in Japanese. These are a special type of word that do not conjugate. This means that they will always appear in the same form. その
comes from the same family of words as それ
, and is used to identify a ‘thing’ that is near the listener.
Is that puzzle hard? (If a sentence finishes in a rising tone, questions markers like ですか may be dropped in casual speech)
That story is definitely a lie.
As the name ‘pre-noun adjectival’ suggests, these words will always appear before a noun, and describe that noun in some way.