Answer:
The removal of one chlorine atom and addition of one fluorine atom.
Step-by-step explanation:
When GeCl4 is transformed into GeCl3F by a substitution process, the main change that is occur in GeCl4 is the removal of one chlorine atom and addition of one fluorine atom. This process is known as substitution process in which two molecules exchange their atoms with each other when they comes in physically contact with each other.