Three statements are given followed by three conclusions (I), (II) and (III). You have to take these statements to be true, even if they seem to be at variance from commonly known facts. Decide which of the given conclusions logically follow(s) from the given statements.​
Statements:​

All keys are locks.

Some locks are doors.

No door is room.
Conclusions:​

(I) Some rooms are keys

(II) Some doors are keys

(III) No room is a key

All keys are locks.

Some locks are doors.

No door is room.

Keys are locks, and no door is a room.
There is no link given between rooms and keys.
So, this conclusion does not definitely follow.

Conclusion (II): Some doors are keys
We know some locks are doors, and all keys are locks.
But it is not given that keys are among those locks which are doors.
So, this conclusion does not follow.

Conclusion (III): No room is a key
Keys are locks, some locks are doors, and no door is a room.
So, keys cannot be rooms.
This conclusion follows.

Final Decision:
Conclusion (I) and (III) are contradictory.
Since (III) is true, the correct choice is: