Which of the foll A. The coordination number is 12

B. It has 74% packing efficiency

C. Octahedral voids of the second layer are covered by spheres of the third layer.

D. In this arrangement, the third layer is identical to the first layer.

Hexagonal close-packing can be arranged by two layers A and B placed one over another which can be represented by the following diagram:

Here, we can say that the second and third layers are not exactly aligned. So statement (iii) is not correct. Only the first and third layers are identical A-A or B-B. So options (i),(ii) and (iv) are correct.