A6？ B5？ C6？ Pentane quaternary amine bromide

You see, both A and C are six, which is obviously inappropriate.

2, so the idea of this problem is to divide the area blocks.

As shown in the figure, the number of blocks divided in sequence in the original problem is 3, 4, 5 and 6.

And all four options are A6 gears? B6？ C7？ C6 block

So, the topic is C.