Explanation:

Correct answer is (e). Statement I is incorrect since the reason that the Police are not going to adopt a law will not make it ineffective. The Police have to take cognizance of the law and it is not their prerogative to judge any law passed by the Parliament. These two statements given cannot share the cause and effect relationship required for connecting them with the given connector ‘since’.
Statement II is not correct since there should be cause and effect relationship between the given statements in order to connect them with the given connector ‘as’. In these sentences, no such relationship is there because a law cannot be ineffective if the Police are not practicing it but they have to abide by it. Had it been the case that the law cannot be implemented, it would have been ineffective as stated in the sentences but so is not the case in this context.
Statement III is also incorrect because it is completely out of context to even think about connecting the given two statements with the connector ‘scarcely’ which actually implies barely. It has no bearing on the given two statements as far as connecting them is concerned. Hence, none of the given choices will be correct in the given context. This makes option E the correct choice among the given options.