A. setTimeout ('formatName', 5000, 'John", "Doe');
=> 'John", "Doe' is wrong

B. setTimeout (formatName('John', ''Doe'), 5000);
''Doe' is wrong

C. setTimout(() => { formatName("John', 'Doe') }, 5000);
"John' is wrong

A and C are correct

C is correct I tested it.

Option C is correct .
function formatName(fname, lname) { console.log(fname + lname)}
setTimeout(() => { formatName('John', 'Doe') }, 5000);

None of this above. According to this https://stackoverflow.com/a/13148281/2661069 no parameters can be passed to function so it should be almost A but the function name should not be a string.
Check it with node:
function formatName(fname, lname) { console.log(fname + lname)}
setTimeout (formatName, 5000, 'John', 'Doe');

B is correct

C is correct