Why are members of European Union fearing Britain’s decision to leave the European Union?

Question

A(They are not concerned at all about it
B(They are worried that Britain will create its own Union
C(They are for that other Countries will follow Britain and leave the European Union
D(they Fear that Britain will no longer trade or sell goods to members of the European union

Answer 1

C(They are worried that other countries will follow Britain and leave the European Union.