the shortstop
In most cases, the second baseman will be covering 2nd base on a hit or fly out to LF.
second base man- as long as the outfielders throw was decnt and in his range. if not, well the outfielder.
That depends on where the 1st baseman fields the ball. If the 1st baseman can field the ball, throw to second, and have enough time to get safely back to the base to catch the return throw, then (s)he will cover. If not, then it is the responsibility of the pitcher.
Second, short, third. Repeat.
That would depend on the team and the manager. Most likely the third or first baseman, but in reality, whoever's in the best position to do so given the game situation at the time. Also, it would not be a stolen base to advance on a pass ball.
if the out would be the third no, it is up to the descrestion of the scorekeeper for example, if there was a runner on third with one out and you bunted the and the third baseman overthrew first, then it would be an rbi, but if the second baseman missed the throw to the first baseman with two outs, then there would be no rbi
He throws it to the 3rd baseman.
Nope. It's a stolen base.
75 mph
That would depend on 'who' is trying to throw the runner out. This answer will assume the questioner is asking about a stolen base and the 'who' is the catcher. The defensive player that covers second base on a steal attempt is the player that the defense believes is on the side of the field that the ball will NOT be hit to. Factors that go into this decision are whether the batter is righthanded or lefthanded, where the pitcher is going to pitch the ball (inside or outside), and how good of a batter the player is (whether they can hit the ball to all fields, whether they are a pull hitter). Generally, if the batter is righthanded and the pitcher is going to pitch inside the odds are better, if the batter makes contact with the ball, that it will be hit to the left side of the field. In this case, it will be the second baseman's responsibility to cover the base if the runner attempts to steal. If the batter is lefthanded and the pitcher is going to pitch inside the odds are better, if the batter makes contact with the ball, that it will be hit to the right side of the field. In this case, it will be the shortstop's responsibility to cover the base if the runner attempts a steal. The decision of who will cover second base on a steal attempt is made before every pitch. On one pitch the second baseman may be the player to cover and on the next pitch the shortstop may be the player to cover. If you are at a game, you may notice when a player is on first base that the second baseman will put his glove up to his face and look at the shortstop just before a pitch is made. The second baseman is giving a signal to the shortstop as to who will cover second base on a steal attempt. Usually, the signal is an open mouth or closed mouth. If the second baseman looks at the shortstop and his mouth is open, this means the second baseman will be the player to cover if a steal is attempted; if the mouth is closed the shortstop will cover. Or vice versa ... it all depends on how the team has set up their signals.
yes
No, if there is a runner on first and the second baseman fields the ball and throws it to the shortstop, who muffs the play and allows both the runner and batter to advance/reach safely, the play would be ruled a fielder's choice and an error. It would still count as an at-bat and a non-hit for the batter, just as if the second-baseman had muffed the throw to the first-baseman with nobody on base.