in the following sentences:<br/>They were <font color="#ff0000">on </font>the bus/<font color="#ff0000">on</font> the boat/<font color="#ff0000">on</font> the airplane/<font color="#ff0000">on</font> the train/<font color="#ff0000">on</font> the bi-cycle<br/><br/>why they used "in" in the following sentenses.why not use "<font color="#ff0000">on</font>".and why did they use "<font color="#ff0000">on"</font> in the above instead of "in"<br/><br/>they were <font color="#ff0000">in </font>the car/<font color="#ff0000">in</font> the taxi.<br/><br/>thank you.<br/>