There is a lot of discussion in PT about EV (expected value), what constitutes +EV and the obvious benefits of finding bets that have +EV. What does it really mean though?

Suppose you have a bankroll of USD 10,000 and I offer you three options for a single bet on a (fair) coinflip.

1) I offer you odds of +120 (+EV of 10.0%) but you must wager all of your bankroll.

2) I offer you odds of +110 (+EV of 5.0%) but you must wager 10% of your bankroll

3) I offer you odds of +105 (+EV of 2.5%) but you must wager 2% of your bankroll

Which one(s) of these would be a smart bet and why?