The main benefit obtained by pair programming stems from the fact that $...$

$$ The productivity of the pair will be higher than the sum of productivities of individual programmers.

$$ The quality of the code produced by the pair will be higher than that of the code produced by

individual programmers.

$$ The actual time spent working on the project will increase since neither of the programmers will

be able to spend time browsing the Internet, reading emails, and doing other things that do not

contribute to the project.

$$ None of the above, there is no benefit at all.