Root-mean-square (r.m.s.) speed of the molecule =
If mass is a constant, N (number of molecule) are also constant, so the variable is pV.
(1): From pV = nRT, when temperatue increase, the pV is also increase, then r.m.s. speed is increased, so (1) is ture
(2): When V increase(expand) and p keep unchanged, pV will be increased, so r.m.s. speed is increased and (2) is also correct
(3): From pV = nRT, temperature keep constant, then the pV also is a constant, so r.m.s. speed will unchange and (3) is false