Statements: No circles are squares. Some squares are triangles. Conclusions: I. Some triangles are not circles. II. No triangle is a circle.

Correct — A.
Rule: 'Some A are B' + 'No B is C' gives 'Some A are not C'.

Some squares are triangles, so some triangles are squares.
No circle is a square, so those triangles are not circles.
So some triangles are not circles: I follows.

II does not: triangles outside the squares may still be circles, and nothing forbids it. Only I follows → option (a).

Why the others are wrong

• (b)
  Only II follows — Only II gets both wrong. II is not forced, since triangles outside the squares may be circles, and I is forced by the triangles that are squares.
• (c)
  Both I and II follow — Both fails on II. 'No triangle is a circle' needs every triangle kept apart from circles, but the statements separate only the triangles inside squares.
• (d)
  Neither I nor II follows — Neither misses I. Triangles that are also squares cannot be circles, because no square is a circle, so some triangles are certainly not circles.

A conclusion follows only if it is true in every diagram the statements allow.

Draw the squares and circles apart, since no circle is a square. Then overlap the triangles with the squares. The triangles in that overlap can never be circles, so 'Some triangles are not circles' is definite.

The other triangles are unconstrained: they may or may not reach the circles. 'No triangle is a circle' is only possible, and a possibility is not a conclusion that follows.

Key facts

• 'Some A are B' also means 'Some B are A'.
• 'Some A are B' + 'No B is C' → 'Some A are not C'.
• A 'No …' conclusion needs the statements to keep the two groups fully apart.

Common traps

• Accepting II because your first diagram happens to keep triangles and circles apart, when another valid diagram lets them overlap.
• Missing I because no statement names triangles and circles together, though the link runs through the squares.

No directly related past PYQ was found.