A polypeptide 10 amino acids long is split into various smaller fragments, and the amino acid sequences of some of the fragments are determined. The identified fragments include: ala-gly-ser-gln, lys-trp-arg-pro, gln-his-lys, asp-ala-gly. What is the primary sequence of the polypeptide?

A. ala-gly-ser-gln-lys-trp-arg-pro-gln-his

B. asp-ala-gly-ser-gln-his-lys-trp-arg-pro

The four fragments have been assembled into the correct sequence.

C. ala-gly-ser-gln-his-lys-trp-arg-pro-asp

D. lys-trp-arg-pro-gln-his-lys-asp-ala-gly

E. none of these