DRAG DROP
You are developing an application by using JavaScript.
You must write a function that returns the sum of the variables named v1, v2, v3, v4.
You need to complete the sum function.
How should you complete the relevant code? (To answer, drag the appropriate code
segment or segments to the correct location or locations in the answer area. Use only code
segments that apply.)
Answer: 
this does not make any sense, anyone can explain?
okay, this looks like another question testing if you think in way as author place the question. V3 and v4 is specified “somehwere” already. I suppose , these are public so should be accessible via this.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call