ask the landlord - do you pay for utilities?

If you have the hookup for electric you could do either. Gas dryers last longer, though

Look and see if you have the outlet for a gas dryer. Its gonna be a big plug. 220 volts

Unless there is a dedicated high capacity 240V outlet installed where your dryer is, buying another gas one will be easier as that line would have to be installed. Depending on the electric service to the house, there may not even be room to add the line to the panel. It could cost many hundreds to install in addition to buying the dryer.

an electric dryer requires proper electrical service ... 220 volt, 40 amp in my community. if that isn't installed already, you have to buy gas

He is just buying himself some cheap insurance ( pipe cap) against someone opening the valve. I assume, that if you get another drier he would help install it to his satisfaction. I t sounds like you are afraid of your landlord.. I don;t know your landlord.

Who owns the dryer? If the dryer came with the unit, the LANDLORD should be buying a replacement.

If you actually supplied the dryer, and there is an electric dryer hookup, you should be able to use either.

Yes, you can. If you get electric you will have to install in electrical outlet for the electric dryer. Depending upon whether you do it your self or hire it done, it will probably cost $100-$2000 depending upon how hard it is and how long the run is.

i would ask your landlord this question

You will need the proper outlet and enough electric capacity to handle the extra load.