To muddy the waters a little(!!)
Generally, speaking, saying ice has high or low conductivity is placing it on some kinda absolute scale, which makes no sense.
But seems clear the answer they want is B, as in it has a sufficiently low thermal conductivity.
Here's a list from hyperphysics..... materials by thermal conductivity:
Look at where snow is on the hyperphysics list. So an igloo is more like a bivouac, really, with a hard outer shell.