MCQ on why lysosomes don't digest themselves

[fantic]

Lysosomes contain very powerful digestive enzymes that can break down proteins, carbohydrates and other molecules. Why don't these enzymes digest the cell itself?
(a) The enzymes will only digest foreign material
(b) The enzymes are separated from the cytoplasm by the lysome's membrane
(c) The enzymes are inactive until secreted from the cell

Tried googling but wasn't of any use. Please help! I'm thinking it's either A or C

[JackBean]

and how do you think the enzymes distinguish, whether is the material foreign or home-made?
I though that lysosome enzymes work inside the cell.

[zombiesagan]

You might want to look into the pH requirements of lysosome enzymes as well and compare the pH of the lysosome with that of the cytoplasm. Of course, to keep these pH's different, the lysosome is separated from the cytoplasm by a strong membrane, although I'm not sure this is what the question is getting at.