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 conclusions logically follow(s) from the statements.

Statements:
Some shells are pebbles.
All pebbles are rocks.

Conclusions:
I. No shell is a rock.
II. Some shells are rocks.

A

Only conclusion I follows

B

Neither conclusion I nor II follows

C

Both conclusions I and II follow

D

Only conclusion II follows