A T flip-flop can be converted in to a D flip-flop by introducing an inverter in the conductor that links the j and k terminals in the T flip-flop.
ya its true that we convert the j-k flip flop into s-r flip by using basic gates
This webpage have a detailed instruction on how to convert a D flip flop to a JK flip flop: Link: http://www.play-hookey.com/digital/converting_ff_inputs.html
it will be the X-OR gate of D and the output Q
we can convert S-R flip flop very easily by neglecting the s-terminal