The Meissner effect

1. increases field strength outside a superconductor
2. breaks flux conservation inside a superconductor
3. is indistinguishable from superdiamagnetism
4. results from zero resistance

NOTE: While I believe that the intended answer is C, I think that A would normally be correct as well.  In any case, it would be a good idea to spend 3 minutes learning what the Meissner effect is.