In the Section "Investigating Life: Did a Myosin Gene Mutation

In the section "Investigating Life: Did a Myosin Gene Mutation Make Humans Brainier?",why would a two base pair deletion in the human myosin gene studied cause it to be nonfunctional?

A) The two base pairs that were missing encoded two amino acids that were essential for the protein to function.
B) The two base pairs that were missing were essential for the protein to function.
C) It introduces a frameshift resulting in a truncated protein.
D) It introduces a substitution mutation that changes the amino acid encoded by that codon.
E) It introduces a silent mutation that changes the amino acid encoded by that codon.