Chromosomal pair possible in metaphase - I
The correct answer is 8 as given by the formula 2n , where n is the number of chromosome in haploid cell.

Explanation:

During prophase 1, synapsis take place as a result of which bivalents are formed. Now each bivalent can arrange itself in two possible manner ( known as independent orientation). Since in this question there are 6 chromosomes which means 3 bivalents, the possible number of arrangement is 2 &times; 2 &times; 2 = 8

The photo here explain independent orientation in a cell having two chromosome pair. You can work this out for 3 chromosomal pair as well.

Your doubt:

As far as I can understand your doubt is that arrangement one is actually same as arrangement third ( with reference to the photo). Well, it might seem like this but if you look carefully the two non homologous chromosomes are arranged in different manner in them .. relative to each other and the homologous partner. And hence the whole arrangement is considered as different arrangements and not the same.

Thus, for 3 chromosomal pair, there are 8 possible arrangement of homologous chromosomes which could occur during metaphase-I.