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A circle is drawn inside a larger circle. If B and C are points on the smaller circle, and A and D are points on the larger circle, are the two circles concentric?
(1) A, B, C, and D all lie on the same line.
(2) AD is a diameter in the larger circle, and BC is a diameter in the smaller circle.
The OA is E.
1+2 is not sufficient.
B can be slightly away from A, and C can be the center point of the big circle. It might satisfy all conditions, but still not be concentric.
Has anyone another strategic approach to solving this DS question? Regards!













