Read the given statements and conclusions carefully. Assuming that the information given in the statements is true, even if it appears to be at variance with commonly known facts, decide which of the given conclusions logically follow(s) from the statements.
Statements:
1. Some pens are sketch.
2. No sketch is colour.
3. All colours are water.
Conclusions:
I. No pen is water.
II. Some sketches are water.
III. Some water is not sketch.

​Statements:
1. Some pens are sketch.
2. No sketch is colour.
3. All colours are water.

​Conclusions:
I. No pen is water. (False, some pens are sketches, but sketches are not colours, and colours are water. So, we cannot conclude that pens are not water).
II. Some sketches are water. (False, there is no direct or indirect relation between sketches and water).
III. Some water is not sketch. (True, all colours are water, and no sketch is colour, so all colours which are water are definitely not sketches).

So, ​Only III conclusion follows.

Thus, correct option is (a).