Which statement about the electron-cloud model is true?
a> it is the currently accepted atomic model.
b> it can easily be replaced by existing models.
c> it specifies the location and momentum of an electron.
d> it does not explain the formation of emission lines.

I believe the correct answer is A. The electron-cloud model is the currently accepted atomic model. In this model, the electron position cannot be specifically known. It is only the probability of being at some point that can be known. This was proposed by Erwin Schrödinger.

The phase where ice changes directly to gas is called sublimation