You are managing the implementation of ERP software in a factory. Software support must be provided round the clock. You need to schedule the shifts of the crew in such a way that a crew cannot finish their shift until next shift crew has arrived. What type of dependency exists between the shifts?

I have answered as "Finish to Start".

My justification :- Predecessor is "First Crew" Successor is "Next shift Crew"

But the correct answer is "Start to Finish"

Can someone explain this ?