An Intern from the United Kingdom Was Working in an American

An intern from the United Kingdom was working in an American software company during summers. One day her boss gave her a memo asking her to post it, with the intention of having it put on the bulletin board. To her boss's surprise the letter was mailed by the intern since the word "post" means "mail" in British English. In communication terms this error can be attributed due to:

A) syntax.
B) phonology.
C) morphology.
D) semantics.
E) semiotics.