Conclusions: Some Circles are Triangles. Some Squares being Circles is a possibility. All Triangles are Circles.

1) All Triangles are Cubes (A) + All Cubes are Circles (A) → All Triangles are Circles (A) → Conversion → Some Circles are Triangles (I). Hence conclusion I and III follow. Some Cuboids are Circles (I) → Conversion → Some Circles are Cuboids (I) + Some Cuboids are Squares (I) → Probable conclusion → Some Squares may be Circles (I). Hence conclusion II follows. Hence option 1 is correct. 2) All Triangles are Cubes (A) + All Cubes are Circles (A) → All Triangles are Circles (A) → Conversion → Some Circles are Triangles (I). Hence conclusion I and III follow. Some Cuboids are Squares (I) → Conversion → Some Squares are Cuboids (I) + All Cuboids are Circles (A) → Some Squares are Circles (I). Hence conclusion II does not follow. Hence option 2 is not correct. 3) Some Triangles are Cubes (I) + Some Cubes are Circles (I) → No conclusion. Hence neither conclusion I nor III follow. Some Cuboids are Squares (I) → Conversion → Some Squares are Cuboids (I) + All Cuboids are Circles (A) → Some Squares are Circles (I). Hence conclusion II does not follow. Hence option 3 is not correct. 4) No Triangle is a Cube (E) + No Cube is a Circle (E) → No conclusion. Hence neither conclusion I nor III follow. Some Cuboids are Squares (I) → Conversion → Some Squares are Cuboids (I) + All Cuboids are Circles (A) → Some Squares are Circles (I). Hence conclusion II does not follow. Hence option 4 is not correct.