Please help to crack

GmatKiss wrote:I would like to thank whoever it was that wrote that piece of music: it has given me so much pleasure.

A. I would like to thank whoever it was that wrote that piece of music:
B. I would like to thank whomever it was that has written that piece of music:
C. I would like to thank whomever it might be that wrote that piece of music:
D. Whoever it was that wrote that piece of music, I would like to thank because
E. I would like to thank whoever it was that wrote that piece of music,

OA after some discussion

crick wrote:Don't we need a semi-colon ( ; ) instead of the colon here ( : ) ?

Crick