In this question, two statements are given, followed by two conclusions numbered I and II. Assuming the statements to be true, even if they seem to be at variance with commonly known facts, decide which of the conclusion(s) logically follows/follow from the statements.

Statements:

I. All stones are pebbles.

II. Some stones are gems.

Conclusions:

I. All gems are pebbles.

II. Some pebbles are stones.​​

I. All stones are pebbles.

II. Some stones are gems.

I. All gems are pebbles. (Not follows, we cannot conclude that all gems are pebbles because the gems that are not stones may not necessarily be pebbles.)

II. Some pebbles are stones. (Follows, From the first statement, we know that all stones are pebbles. Therefore, it is logically correct to say that some pebbles (the stones) exist.
​Only conclusion II follows.

​Thus, correct option is (d).