Author: Bella (Songshan) Guo
There are only limited choices for filling the blanks, especially since some of the four-Morse-symbol possibilities are not letters:
dash ___ ___ dot: B, C, or Z
___ dash dot: G or R
___ dot: I or N
dash ___ dash ___: C or Y
dash dot ___: D or K
The only words this can form are CRICK and BRICK, but BRICK doesn't have enough dashes, so the answer is CRICK.
C = dash dot dash dot
R = dot dash dot
I = dot dot
C = dash dot dash dot
K = dash dot dash