Read the given statements and conclusions carefully. You have to consider the given statements to be true even if they seem to be at variance from commonly known facts. You have to decide which of the given conclusions logically follow/s from the given statements.
Statements:
I. Some nouns are pronouns.
II. All pronouns are adjectives.
III. No adjective is an adverb.
Conclusions:
(I) : No pronoun is an adverb.
(II) : At least some nouns are adverbs.

​Statements:
I. Some nouns are pronouns.
II. All pronouns are adjectives.
III. No adjective is an adverb.

​Conclusions:

(I) : No pronoun is an adverb. (Follows, because of  No adjective is an adverb.)
(II) : At least some nouns are adverbs. (Not follows, there is no any relation between noun and adverb)

So, Only conclusion (I) follows.

Thus, correct option is (c).