bulk,drain ,source,gate in cmos
I think your explanation is correct. My explanation is that the reverse bias on the source-to-substrate junction reduces the amount of charge in the channel for a given gate-to-source bias. Alternatively stated, it increase the gate voltage needed to induce a given number of mobile carriers in the channel, that is, it increase the threshold voltage. so it is more difficult to turn on the mosfet when taking body effect into account. By the way, in integrated circuits, we should consider the mosfet as a five terminal device: drain, source, gate, substrate, and the bulk.